media: rockchip/rga: annotate PM functions as __maybe_unused

The newly added driver has incorrect #ifdef annotations on its
PM functions, leading to a harmless compile-time warning when
CONFIG_PM is disabled:

drivers/media/platform/rockchip/rga/rga.c:760:13: error: 'rga_disable_clocks' defined but not used [-Werror=unused-function]
 static void rga_disable_clocks(struct rockchip_rga *rga)
             ^~~~~~~~~~~~~~~~~~
drivers/media/platform/rockchip/rga/rga.c:728:12: error: 'rga_enable_clocks' defined but not used [-Werror=unused-function]

This removes the #ifdef and marks the functions as __maybe_unused,
so gcc can silently drop all the unused code.

Fixes: f7e7b48e

 ("[media] rockchip/rga: v4l2 m2m support")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>