[media] saa6752hs: Convert to devm_kzalloc()

Using the managed function the kfree() calls can be removed from the
probe error path and the remove handler.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>