i965: Remove unnecessary walk through Mesa IR in ProgramStringNotify().

i965: Remove unnecessary walk through Mesa IR in ProgramStringNotify().

Variable indexing of non-uniform arrays only exists in GLSL.  Likewise,
OPCODE_CAL/OPCODE_RET only existed to try and support GLSL's function
calls.  We don't use Mesa IR for GLSL, and these features are explicitly
disallowed by ARB_vertex_program/ARB_fragment_program and never
generated by ffvertex_prog.c.

Since they'll never happen, there's no need to check for them, which
saves us from walking through all the Mesa IR instructions.

Reviewed-by: Eric Anholt <eric@anholt.net>