meta: Eliminate samplers[] array in favor of using vec4_prefix.

meta: Eliminate samplers[] array in favor of using vec4_prefix.

We don't need an array mapping the shader index to "sampler2DMS",
"isampler2DMS", and so on.  We can simply do "%ssampler2DMS" and pass in
vec4_prefix, which is "", "i", or "u".

This eliminates the use of C99 array initializers and should fix the
MSVC build.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75344
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>