[aes] Masked GHASH implementation

[vogelpi]

This PR contains the initial RTL for the masked GHASH implementation.

The design is functionally correct and passes first masking verification experiments. This means we shouldn't consider the masking verification done yet but we can be reasonably confident that the design will not need to be radically changed.

[nasahlpa]

Are you planning to add the documentation to this PR or will this be added later? It would help reviewing the PR, but from a first look it looks good to me.

[vogelpi]

I am currently writing the documentation for this but it will be in a separate doc for the time being.

[vogelpi]

CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_control_fsm.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_core.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_ctrl_gcm_reg_shadowed.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_ghash.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_pkg.sv

This PR touches AES RTL files but this is expected.

[nasahlpa]

I had a more thorough look into the masking and I think it looks good.

[nasahlpa]

CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_control_fsm.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_core.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_ctrl_gcm_reg_shadowed.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_ghash.sv
CHANGE AUTHORIZED: hw/ip/aes/rtl/aes_pkg.sv

This PR touches AES RTL files but this is expected.

[vogelpi]

Thanks you both for your reviews. I'll share the spec as soon as it's ready. I am merging this now.