Testsuite/Fortran: gfortran.dg/pr96711.f90 - fix expected value for PowerPC [PR96983]

gcc/testsuite/ChangeLog:

	PR fortran/96983
	* gfortran.dg/pr96711.f90: Use 2**digit(x) instead of a hard-coded value;
	add comments regarding what the code does.

(cherry picked from commit 9e0a5e3ea37f9d7d2b6f2dab7c0bfbeaf08466a3)
1 file changed