mesa: add additional checks for uniform location query

mesa: add additional checks for uniform location query

Patch adds additional check to make sure we don't return locations for
structures or arrays of structures.

From page 79 of the OpenGL 4.2 spec:
    "A valid name cannot be a structure, an array of structures, or any
    portion of a single vector or a matrix."

v2: use without-array() to simplify code (Timothy)

No Piglit or CTS regressions observed.

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>