Clarify apparent inconsistency of debug version read by registers

[psherman42]

There are two separate four-bit register fields where debug specification version can be determined. Both register fields have their own usefulness and advantages. However, these two register fields use different definitions for what their field values mean in terms of the debug specification version number. It would be very nice, somewhere near beginning of the Specification Document, to define the version field and clearly show both register fields with their values in one place.

Reading debug version from DM at address 0x11 (Table 3.8):
dmstatus[3:0]=version (0=na, 1=0.11, 2=0.13, ..., 15=tbd) -- see Section 3.12.1

Reading debug version from JTAG TAP address 0x10 (Table 6.1):
dtmcs[3:0]=version (0=0.11, 1=0.13, ..., 15=tbd) -- see Section 6.1.4

Advantage of the former is helpful once Debug Module communication has been established.
Advantage of the latter is helpful at the very beginning of interaction with Debug Transport Module, or when one desires not to, or cannot, communicate with a busy Debug Module.