fbdev: bfin-t350mcqb-fb: fix fbmem allocation with blanking lines

The current allocation does not include the memory required for blanking
lines.  So avoid memory corruption when multiple devices are using the DMA
memory near each other.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>