graphics/mesa-devel: unbreak build on aarch64 after cde5539d63d4

In file included from ../src/panfrost/perf/pan_perf.c:15:
../src/panfrost/perf/pan_perf.h:51:11: error: use of undeclared identifier 'CLOCK_MONOTONIC_RAW'

51 |    return CLOCK_MONOTONIC_RAW;
   |           ^

Reported by: pkg-fallout