drm/xe/pm: Assert on runtime suspend if VFs are enabled

drm/xe/pm: Assert on runtime suspend if VFs are enabled

We hold an additional reference to the runtime PM to keep PF in D0
during VFs lifetime, as our VFs do not implement the PM capability.
This means we should never be runtime suspending as long as VFs are
enabled.

v8: Add !IS_SRIOV_VF() assert (Matthew Brost)

Suggested-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patch.msgid.link/20251030122357.128825-4-raag.jadav@intel.com