media: sun4i-csi: Fix 'Unbalanced pm_runtime_enable!'

When removing the module, balance PM runtime enable with
the corresponding disable call.

Signed-off-by: Oleg Verych <olecom@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>