mesa: need to check resource and set length even if bufSize is 0

mesa: need to check resource and set length even if bufSize is 0

This fixes a number of dEQP tests, such as:

dEQP-GLES31.functional.program_interface_query.buffer_limited_query.resource_query

It was expecting the length to be set even in the bufSize == 0 case.
Also _mesa_get_program_resourceiv does some error checking on the
resource which should probably happen even in the bufSize == 0 case as
well although there's no dEQP test for that.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>