rs6000: Improve p9-dimode* testcases

rs6000: Improve p9-dimode* testcases

This removes the unnecessary restriction to 32-bit (all three ways).
It also scans for mtvsr*, not just mtvsrd.  Finally, it uses the "wa"
constraints instead of "wi" in the inline asm statements.

gcc/testsuite/
	* gcc.target/powerpc/p9-dimode1.c: Don't restrict to -m64.  Check for
	all mtvsr*, not just mtvsrd.  Use "wa" instead of "wi" constraints.
	* gcc.target/powerpc/p9-dimode2.c: Ditto.

From-SVN: r271696