replace _mesa_is_pow_two with util_is_power_of_two_*

Mostly this uses util_is_power_of_two_or_zero, which has the same
behavior as _mesa_is_pow_two when the input is zero. In cases where the
value is known to be != 0 ahead of time I used the _nonzero variant as
it may be faster on some platforms.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3024>

src/intel/compiler/brw_reg.h

@@ -986,7 +986,7 @@ static inline struct brw_reg
 spread(struct brw_reg reg, unsigned s)
 {
    if (s) {
-      assert(_mesa_is_pow_two(s));
+      assert(util_is_power_of_two_nonzero(s));
 
       if (reg.hstride)
          reg.hstride += cvt(s) - 1;

src/intel/compiler/brw_vec4_generator.cpp

@@ -2064,8 +2064,7 @@ generate_code(struct brw_codegen *p,
           *
           * where they pack the four bytes from the low and high four DW.
           */
-         assert(_mesa_is_pow_two(dst.writemask) &&
-                dst.writemask != 0);
+         assert(util_is_power_of_two_nonzero(dst.writemask));
          unsigned offset = __builtin_ctz(dst.writemask);
 
          dst.type = BRW_REGISTER_TYPE_UB;