[media] stk1160: Try to continue with fewer transfer buffers

Many people are trying to use stk1160 on low memory devices.
Instead of failing if one allocation fails, we allow the driver
to continue working if fewer transfer buffers are available.

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>