Minor fixup and adding a few missed functions

[RobertZ2011]

Fixup a few minor things that didn't get caught in the initial implementation.

[felipebalbi]

Doesn't compile when only log feature is enabled:

❯ git status
On branch minor-changes
Your branch is up to date with 'origin/minor-changes'.

nothing to commit, working tree clean

❯ cargo build --no-default-features -F log
   Compiling tps6699x v0.1.0 (D:\workspace\odp\tps6699x)
error[E0277]: `command::ReturnValue` doesn't implement `Display`
   --> src\asynchronous\fw_update.rs:158:86
    |
158 |                 info!("Controller {}: Failed to initialize FW update, result {}", i, r);
    |                                                                                      ^ `command::ReturnValue` cannot be formatted with the default formatter
    |
    = help: the trait `Display` is not implemented for `command::ReturnValue`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
    = note: this error originates in the macro `$crate::__private_api::format_args` which comes from the expansion of the macro `info` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `command::TfuqBlockStatus` doesn't implement `Display`
   --> src\asynchronous\fw_update.rs:194:87
    |
194 |                 error!("Controller {}: Header block validation failed, result {}", i, r);
    |                                                                                       ^ `command::TfuqBlockStatus` cannot be formatted with the default formatter
    |
    = help: the trait `Display` is not implemented for `command::TfuqBlockStatus`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
    = note: this error originates in the macro `$crate::__private_api::format_args` which comes from the expansion of the macro `error` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `command::TfuqBlockStatus` doesn't implement `Display`
   --> src\asynchronous\fw_update.rs:295:80
    |
295 |                 error!("Controller {}: Block validation failed, result {}", i, r);
    |                                                                                ^ `command::TfuqBlockStatus` cannot be formatted with the default formatter
    |
    = help: the trait `Display` is not implemented for `command::TfuqBlockStatus`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
    = note: this error originates in the macro `$crate::__private_api::format_args` which comes from the expansion of the macro `error` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.
error: could not compile `tps6699x` (lib) due to 3 previous errors

[RobertZ2011]

Currently needs OpenDevicePartnership/embedded-usb-pd#3 to build.

[RobertZ2011]

Checks are failing due to permissions with embedded-usb-pd, but I ran tests and built examples locally. Going to merge, both this crate and embedded-usb-pd are stated to become public in the next round so hopefully this will be one of the last PRs that will need a bypass.