glsl: avoid calling base_alignment when samplers are involved

glsl: avoid calling base_alignment when samplers are involved

Earlier commit 53bf7c8fd2e changed the logic to always call
base_alignment on structs. 1ec715ce8b12 hacked the function to return 0
for sampler fields, but didn't handle sampler arrays. Instead of
extending the hack, avoid calling base_alignment in the first place on
non-UBO uniforms.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89726
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Tapani Palli <tapani.palli@intel.com>