Force long double to be IBM 128-bit on PowerPC test, PR target/70117.

Force long double to be IBM 128-bit on PowerPC test, PR target/70117.

This patch fixes the pr70117 test to use IBM 128-bit long double.

I have run tests on a little endian power9 system with 3 compilers.  There
were no regressions with these patches, and the two tests in the following
patches now work if the default long double is not IBM 128-bit:

    *	One compiler used the default IBM 128-bit format;
    *	One compiler used the IEEE 128-bit format; (and)
    *	One compiler used 64-bit long doubles.

I have also tested compilers on a big endian power8 system with a compiler
defaulting to power8 code generation and another with the default cpu
set.  There were no regressions.

Can I check this patch into the master branch?

gcc/testsuite/
2021-04-28  Michael Meissner  <meissner@linux.ibm.com>

	PR target/70117
	* gcc.target/powerpc/pr70117.c: Force the long double type to use
	the IBM 128-bit format.