glsl/linker: Fix type checks for location aliasing

glsl/linker: Fix type checks for location aliasing

From the OpenGL 4.6 spec, section 4.4.1 Input Layout Qualifiers, Page 68,
(Location aliasing):

   "Further, when location aliasing, the aliases sharing the location
    must have the same underlying numerical type  (floating-point or
    integer)."

The current implementation is too strict, since it checks that the
the base types are an exact match instead.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>