glsl: Delete bogus ir_set_program_inouts assert.

glsl: Delete bogus ir_set_program_inouts assert.

This assertion is bogus.  Varying structs, and arrays of structs, are
allowed by GLSL, and we can see them here.  While we currently don't
have any partial-variable support for those, simply returning false
and marking the entire thing as used is certainly legitimate.

I believe this is often swept under the rug by varying packing,
but that's disabled in certain tessellation situations.

Hit by 20 dEQP-GLES31.functional.tessellation.user_defined_io.* tests.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>