i965: Initialize inout_offset parameter to brw_search_cache().

i965: Initialize inout_offset parameter to brw_search_cache().

Two callers of brw_search_cache() weren't initializing that function's
inout_offset parameter: brw_blorp_const_color_params::get_wm_prog()
and brw_blorp_const_color_params::get_wm_prog().

That's a benign problem, since the only effect of not initializing
inout_offset prior to calling brw_search_cache() is that the bit
corresponding to cache_id in brw->state.dirty.cache may not be set
reliably.  This is ok, since the cache_id's used by
brw_blorp_const_color_params::get_wm_prog() and
brw_blorp_blit_params::get_wm_prog() (BRW_BLORP_CONST_COLOR_PROG and
BRW_BLORP_BLIT_PROG, respectively) correspond to dirty bits that are
not used.

However, failing to initialize this parameter causes valgrind to
complain.  So let's go ahead and fix it to reduce valgrind noise.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66779

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>