[PATCH,RS6000 2/5] Rework the RS6000_BTM defines.

[PATCH,RS6000 2/5] Rework the RS6000_BTM defines.

The RS6000_BTM_<xxxx> definitions are mostly unused after the rs6000
builtin code was reworked.  The remaining references can be replaced
with the OPTION_MASK_<xxxx> and MASK_<xxxx> equivalents.

This patch remvoes the defines:
RS6000_BTM_FRES, RS6000_BTM_FRSQRTE, RS6000_BTM_FRSQRTES,
RS6000_BTM_POPCNTD, RS6000_BTM_CELL, RS6000_BTM_DFP,
RS6000_BTM_HARD_FLOAT, RS6000_BTM_LDBL128, RS6000_BTM_64BIT,
RS6000_BTM_POWERPC64, RS6000_BTM_FLOAT128, RS6000_BTM_FLOAT128_HW
RS6000_BTM_MMA, RS6000_BTM_P10.

I note that the BTM -> OPTION_MASK mappings are not always 1-to-1.
in particular the BTM_FRES and BTM_FRSQRTE values were both mapped to
OPTION_MASK_PPC_GFXOPT, while the BTM_FRE and BTM_FRSQRTES both mapped
to OPTION_MASK_POPCNTB.  In total I spent quite a bit of time
double-checking these since it looked like copy/paste errors.  I split
some of these changes out into a subsequent patch to limit the amount
of potential confusion in any particular patch.

gcc/
	* config/rs6000/rs6000-c.cc: Update comments.
	* config/rs6000/rs6000.cc (RS6000_BTM_FRES, RS6000_BTM_FRSQRTE,
	RS6000_BTM_FRSQRTES, RS6000_BTM_POPCNTD, RS6000_BTM_CELL,
	RS6000_BTM_64BIT, RS6000_BTM_POWERPC64, RS6000_BTM_DFP,
	RS6000_BTM_HARD_FLOAT,RS6000_BTM_LDBL128, RS6000_BTM_FLOAT128,
	RS6000_BTM_FLOAT128_HW, RS6000_BTM_MMA, RS6000_BTM_P10): Replace
	with OPTION_MASK_PPC_GFXOPT, OPTION_MASK_PPC_GFXOPT,
	OPTION_MASK_POPCNTB, OPTION_MASK_POPCNTD,
	OPTION_MASK_FPRND, MASK_64BIT, MASK_POWERPC64,
	OPTION_MASK_DFP, OPTION_MASK_SOFT_FLOAT, OPTION_MASK_MULTIPLE,
	OPTION_MASK_FLOAT128_KEYWORD, OPTION_MASK_FLOAT128_HW,
	OPTION_MASK_MMA, OPTION_MASK_POWER10.
	* config/rs6000/rs6000.h (RS6000_BTM_FRES, RS6000_BTM_FRSQRTE,
	RS6000_BTM_FRSQRTES, RS6000_BTM_POPCNTD, RS6000_BTM_CELL,
	RS6000_BTM_DFP, RS6000_BTM_HARD_FLOAT, RS6000_BTM_LDBL128,
	RS6000_BTM_64BIT, RS6000_BTM_POWERPC64, RS6000_BTM_FLOAT128,
	RS6000_BTM_FLOAT128_HW, RS6000_BTM_MMA, RS6000_BTM_P10): Delete.