st/mesa: use PROGRAM_ARRAY for storing structs containing arrays

st/mesa: use PROGRAM_ARRAY for storing structs containing arrays

Previously, we used PROGRAM_ARRAY only for variables which were
arrays or matrices.  But if the variable is a structure containing
an array or matrix, we need to use PROGRAM_ARRAY for that too.

Before, we failed an assertion:
  state_tracker/st_glsl_to_tgsi.cpp:4900:
  Assertion `src_reg->file != PROGRAM_TEMPORARY' failed.
when running the piglit test
glsl-1.20/execution/fs-const-array-of-struct-of-array.shader_test

Reviewed-by: Marek Olšák <marek.olsak@amd.com>