drm/imagination: make pvr_fw_trace_init_mask_ops static

drm/imagination: make pvr_fw_trace_init_mask_ops static

The pvr_fw_trace_init_mask_ops is not used outside pvr_fw_trace.c
so make it static to avoid the following sparse warning:

drivers/gpu/drm/imagination/pvr_fw_trace.c:74:31: warning: symbol 'pvr_fw_trace_init_mask_ops' was not declared. Should it be static?

Fixes: c6978643ea1c ("drm/imagination: Validate fw trace group_mask")
Reviewed-by: Alessio Belle <alessio.belle@imgtec.com>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Link: https://patch.msgid.link/20260703162338.2848039-1-ben.dooks@codethink.co.uk
Signed-off-by: Alessio Belle <alessio.belle@imgtec.com>