libgomp: Ensure that either gomp_team is properly aligned [PR102838]

struct gomp_team has struct gomp_work_share array inside of it.
If that latter structure has 64-byte aligned member in the middle,
the whole struct gomp_team needs to be 64-byte aligned, but we weren't
allocating it using gomp_aligned_alloc.

This patch fixes that, except that on gcn team_malloc is special, so
I've instead decided at least for now to avoid using aligned member
and use the padding instead on gcn.

2021-11-18  Jakub Jelinek  <jakub@redhat.com>

	PR libgomp/102838
	* libgomp.h (GOMP_USE_ALIGNED_WORK_SHARES): Define if
	GOMP_HAVE_EFFICIENT_ALIGNED_ALLOC is defined and __AMDGCN__ is not.
	(struct gomp_work_share): Use GOMP_USE_ALIGNED_WORK_SHARES instead of
	GOMP_HAVE_EFFICIENT_ALIGNED_ALLOC.
	* work.c (alloc_work_share, gomp_work_share_start): Likewise.
	* team.c (gomp_new_team): If GOMP_USE_ALIGNED_WORK_SHARES, use
	gomp_aligned_alloc instead of team_malloc.