[media] media: ti-vpe: vpe: Return NULL for invalid buffer type

[media] media: ti-vpe: vpe: Return NULL for invalid buffer type

get_q_data can be called with different values for type
e.g. vpe_try_crop calls it with the buffer type which gets passed
from user space

Framework doesn't check wheather its correct type or not
If user space passes wrong type, kernel should not crash.
Return NULL when the passed type is invalid.

Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>