openmp: Improve testsuite/libgomp.c/affinity-1.c testcase

openmp: Improve testsuite/libgomp.c/affinity-1.c testcase

I've noticed that while I have added hopefully sufficient test coverage
for the case where one uses simple number or !number as p-interval,
I haven't added any coverage for number:len:stride or number:len.

This patch adds that.

2021-10-15  Jakub Jelinek  <jakub@redhat.com>

	* testsuite/libgomp.c/affinity-1.c (struct places): Change name field
	type from char [50] to const char *.
	(places_array): Add a testcase for simplified syntax place followed
	by length or length and stride.