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/[e-mail]/

Fixes: e38e8391f30b ("drm/imagination: Use pwrseq for TH1520 GPU power management")
Cc: [e-mail]
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Reviewed-by: Alessio Belle <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Matt Coster <[e-mail]>

drivers/gpu/drm/imagination/Kconfig

···
 	depends on DRM
 	depends on MMU
 	depends on PM
+	depends on POWER_SEQUENCING || !POWER_SEQUENCING
 	select DRM_EXEC
 	select DRM_GEM_SHMEM_HELPER
 	select DRM_SCHED