ARM: OMAP3: PM: cleanup cam_pwrdm leftovers

commit e7410cf7 (OMAP3: PM: move device-specific special cases from PM
core into CPUidle) moved mangement of cam_pwrdm to CPUidle but left
some remnants behind, namely the call to clkcm_allo_idle() for the
clockdomains in the MPU pwrdm.  Remove these since they are not
necessary and cause unwanted latency in the idle path.

Acked-by: Tero Kristo <Tero Kristo <t-kristo@ti.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>