cris: Remove CRIS v32 ACR artefacts

cris: Remove CRIS v32 ACR artefacts

This is the change to which I alluded to this in r11-220 /
d0780379c1b6 as "causes extra register moves in libgcc".  It has
unfortunate side-effects due to the change in register-class topology.
There's a slight improvement in coremark numbers (< 0.07%) though also
increase in code size total (< 0.7%) but looking at the individual
changes in functions, it's all-over (-7..+7%).  Looking specifically
at functions that improved in speed, it's also both plus and minus in
code sizes.  It's unworkable to separate improvements from regressions
for this case.  I'll follow up with patches to restore the previous
code quality, in both size and speed.

gcc:
	* config/cris/constraints.md (define_register_constraint "b"): Now
	GENERAL_REGS.
	* config/cris/cris.md (CRIS_ACR_REGNUM): Remove.
	* config/cris/cris.h: (reg_class, REG_CLASS_NAMES)
	(REG_CLASS_CONTENTS): Remove ACR_REGS, SPEC_ACR_REGS, GENNONACR_REGS,
	and SPEC_GENNONACR_REGS.
	* config/cris/cris.cc (cris_preferred_reload_class): Don't mention
	ACR_REGS and return GENERAL_REGS instead of GENNONACR_REGS.