drm/etnaviv: Fix a leak in submit_pin_objects()

drm/etnaviv: Fix a leak in submit_pin_objects()

BugLink: https://bugs.launchpad.net/bugs/1881178
commit ad99cb5e783bb03d512092db3387ead9504aad3d upstream.

If the mapping address is wrong then we have to release the reference to
it before returning -EINVAL.

Fixes: 088880ddc0b2 ("drm/etnaviv: implement softpin")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>