i965: Silence unused parameter warnings in intel_mipmap_tree.c

i965: Silence unused parameter warnings in intel_mipmap_tree.c

The target parameter of compute_msaa_layout appears to be unused since
83b83fb when support for CMS textures was added for Gen7.

The brw parameter of intel_get_non_msrt_mcs_alignment appears to be
unused since e92fbdc when the GEN check (along with the "can we fast
clear" decision) was moved to a different function.

intel_mipmap_tree.c: In function 'compute_msaa_layout':
intel_mipmap_tree.c:62:73: warning: unused parameter 'target' [-Wunused-parameter]
 compute_msaa_layout(struct brw_context *brw, mesa_format format, GLenum target,
                                                                         ^
intel_mipmap_tree.c: In function 'intel_get_non_msrt_mcs_alignment':
intel_mipmap_tree.c:143:54: warning: unused parameter 'brw' [-Wunused-parameter]
 intel_get_non_msrt_mcs_alignment(struct brw_context *brw,
                                                      ^

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>