[RS6000] PR88346, Inconsistent list of CPUs supported after r266502

[RS6000] PR88346, Inconsistent list of CPUs supported after r266502

This patch removes the %e error for AIX, since it seems there has been
no attempt to keep cpu support up to date for AIX, and adds missing
entries to ASM_CPU_SPEC in rs6000.h.  The rs64a->rs64 name change
happened a long time ago as a fix for PR20813 (git commit c92b4c3f5b).

	PR 88346
	* config/rs6000/rs6000.h (ASM_CPU_SPEC): Correct %e message.  Handle
	-mcpu=rs64, not -mcpu=rs64a.  Handle -mcpu=powerpc64 and -mcpu=titan.
	* config/rs6000/driver-rs6000.c (asm_names): Similarly.
	* config/rs6000/aix71.h (ASM_CPU_SPEC): Delete %e message.  Handle
	-mcpu=rs64, not -mcpu=rs64a.
	* config/rs6000/aix72.h (ASM_CPU_SPEC): Likewise.

From-SVN: r267375