rs6000: Synchronize the --with-cpu list in config.gcc with reality

power, power2, rios, rios1, rios2, rsc, rsc2 support was removed.
rs64a never was a supported option; it's spelled rs64.
power5+ and powerpc64le are supported options but could not be set as
default.


	* config.gcc (supported_defaults) [powerpc*-*-*]: Update.

From-SVN: r245435

gcc/ChangeLog

+2017-02-13  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* config.gcc (supported_defaults) [powerpc*-*-*]: Update.
+
 2017-02-14 Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/79095

gcc/config.gcc

@@ -4260,8 +4260,9 @@ case "${target}" in
 				eval "with_$which=405"
 				;;
 			"" | common | native \
-			| power | power[23456789] | power6x | powerpc | powerpc64 \
-			| rios | rios1 | rios2 | rsc | rsc1 | rs64a \
+			| power[3456789] | power5+ | power6x \
+			| powerpc | powerpc64 | powerpc64le \
+			| rs64 \
 			| 401 | 403 | 405 | 405fp | 440 | 440fp | 464 | 464fp \
 			| 476 | 476fp | 505 | 601 | 602 | 603 | 603e | ec603e \
 			| 604 | 604e | 620 | 630 | 740 | 750 | 7400 | 7450 \