mesa: Use a new, more specific hook for shader uniform changes.

mesa: Use a new, more specific hook for shader uniform changes.

Gallium drivers and i965 don't require special notification when
sampler uniforms change.  They simply see the _NEW_TEXTURE and adjust
their indirection tables.  These drivers don't want ProgramStringNotify:
it simply causes pointless recompiles.

Unfortunately, i915 still requires shader recompiles and needs
ProgramStringNotify.  Rather than trying to fix that, simply change the
hook to a new, more specific one: ShaderUniformChange.  On i915, this
translates to ProgramStringNotify; others simply ignore it.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>