Fix float128-call.c test for power8 IEEE 128 and power10.

Fix float128-call.c test for power8 IEEE 128 and power10.

I built a compiler on a little endian power8 system where the default long
double was IEEE 128-bit instead of IBM 128-bit.  I discovered that on
power8, we would generate a lxvd2x and xxpermdi to deal with the endianess
instead of the Altivec lxv.

In addition, I noticed the constant that was being loaded (1.0q) could be
loaded by the lxvkq instruction.

I rewrote the test to handle all forms of vector load and store that can
be generated.

2021-08-27  Michael Meissner  <meissner@linux.ibm.com>

gcc/testsuite/
	* gcc.target/powerpc/float128-call.c: Fix test for IEEE 128-bit
	long double and power10.