PowerPC64 little-endian fixes: AltiVec tests

PowerPC64 little-endian fixes: AltiVec tests

A couple of AltiVec tests fail spuriously on powerpc64le-linux, because
they compare against an incorrect pattern.  Note that those tests already
contain little-endian variants of the patterns, but those seem to have
bit-rotted a bit: when outputting a vector, GDB no longer omits trailing
zero elements (as it used to do in the past).

This patch updates the pattern to the new GDB output behavior.

In addition, the patch updates the endian test to use the new
gdb_test_multiple logic instead of gdb_expect.

gdb/testsuite/ChangeLog:

	* gdb.arch/altivec-regs.exp: Use gdb_test_multiple for endian test.
	(decimal_vector): Fix for little-endian.