[media] s5p-mfc: Collapse two error message into one

s5p_mfc_alloc_priv_buf() prints two message to report invalid memory
configuration error. Collapse them into a single message.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>