rnn: add headergen2

Modified version of headergen which generates inline fxns for setting
register/bitfield values and 'C' enums for enum values, in order to have
some sort of type safety.  The inline fxns also have asserts for
min/max/align to preserve the error checking.

Possibly the shift handling is wrong for nested bitsets.. I'm not really
using that feature for adreno.
a2xx: add remaining registers

Also, move stuff that is common with a3xx to a common file.
a3xx: use adreno_common.xml