i915, i965: Silence unused parameter warnings in intel_miptree_unmap_gtt

i915, i965: Silence unused parameter warnings in intel_miptree_unmap_gtt

intel_mipmap_tree.c: In function 'intel_miptree_unmap_gtt':
intel_mipmap_tree.c:777:34: warning: unused parameter 'map' [-Wunused-parameter]
    struct intel_miptree_map *map,
                                  ^
intel_mipmap_tree.c:778:17: warning: unused parameter 'level' [-Wunused-parameter]
    unsigned int level,
                 ^
intel_mipmap_tree.c:779:17: warning: unused parameter 'slice' [-Wunused-parameter]
    unsigned int slice)
                 ^

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