meta: Use result of texture coordinate clamping operation

meta: Use result of texture coordinate clamping operation

Previously the result of the complicated clamp() expression just dropped
on the floor: clamp does not modify any of its parameters.  Looking at
the surrounding code, I believe this is supposed to modify the value of
tex_coord.

This change (along with a change to avoid the use of
brw_blorp_framebuffer) does not affect any existing piglit tests.  I'm
not sure what this clamp is trying to accomplish, so I'm not sure how to
write a test to exercise this path.

I also noticed another bug in this code.  There is no way the array
texture case could possibly work.  This will generate code for the
TEXEL_FETCH macro like:

    #define TEXEL_FETCH(coord) texelFetch(texSampler, ivec3(coord), sample_map[int(2 * fract(coord.x))]);

Since the coord parameter of this macro is a vec2 at all invocations, no
expansion of this macro will even compile.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Cc: Topi Pohjolainen <topi.pohjolainen@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>