testsuite: Fix up scan-tree-dump-times regexps for 64-bit targets

The added (?:_ull) match on 32-bit targets, but are equivalent to just
adding _ull into the strings, i.e. require the _ull substrings, while
the intent is that they are optional, so we should use (?:_ull)? instead.

2020-11-11  Jakub Jelinek  <jakub@redhat.com>

	* gfortran.dg/gomp/workshare-reduction-3.f90: Use (?:_ull)? instead
	of (?:_ull) in the scan-tree-dump-times directives.
	* gfortran.dg/gomp/workshare-reduction-26.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-27.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-28.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-36.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-37.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-38.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-39.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-40.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-41.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-42.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-43.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-44.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-45.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-46.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-47.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-56.f90: Likewise.
	* gfortran.dg/gomp/workshare-reduction-57.f90: Likewise.