gpu: pvr: remove unused function args from PVRSRVSetDevicePowerStateKM

gpu: pvr: remove unused function args from PVRSRVSetDevicePowerStateKM

The CallerID parameter was anyway a horrible concept in terms of
understanding what the function is supposed to do when ISR_ID, KERNEL_ID
or TIMER_ID is passed. Function arguments should never have such "high
level" meaning, but rather denote much more concrete things. In this case
for example whether we should mutex_lock() or mutex_trylock() for a
certain lock. Better yet we should have separate functions for the two
cases to keep the function body as simple as possible.

Happily the CallerID and RetainMutex arguments are unused now, so they
can be removed.

Signed-off-by: Imre Deak <imre.deak@nokia.com>
CC: Mark Underwood <mark.underwood@imgtec.com>
CC: Mark Riding <mark.riding@imgtec.com>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@nokia.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@nokia.com>