Revert "raw: move buffer size check up."

This reverts commit cc5dd632cecc5114717d0b90f8c2be162b1c6ee8.
The change was redundant, it has been fixed long ago (422e3a7)

Conflicts:

	libavcodec/rawdec.c

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
