MLK-16812 drm/imx: ldb: Let system PM behave properly when we are unbinded

MLK-16812 drm/imx: ldb: Let system PM behave properly when we are unbinded

The system power management operations should get correct driver data
before going on to further handling.  When the component is unbinded,
driver data should be set to NULL so that the system power management
may be bypassed(return early).  This way, we may prevent the system power
management from using any invalid driver data.

Fixes: 915ac0ad7369 ("MLK-16581-7 drm/imx: ldb: Add system power management support")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
(cherry picked from commit 91033d8707a92e089fbe0b9cb48565d2c8581659)