drm/imagination: Optionally depend on POWER_SEQUENCING

drm/imagination: Optionally depend on POWER_SEQUENCING

When the change using pwrseq was added, I nixed the dependency on
POWER_SEQUENCING since we didn't want it pulled in on platforms where
it's not needed [1]. I hadn't, however, considered the link-time
implications of this for configs with POWER_SEQUENCING=m.

[1]: https://lore.kernel.org/r/a265a20e-8908-40d8-b4e0-2c8b8f773742@imgtec.com/

Fixes: e38e8391f30b ("drm/imagination: Use pwrseq for TH1520 GPU power management")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510111806.CMulNMKW-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202511011739.SONHjSfR-lkp@intel.com/
Reviewed-by: Alessio Belle <alessio.belle@imgtec.com>
Link: https://patch.msgid.link/20251014-pwrseq-dep-v1-1-49aabd9d8fa1@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>