commit 821117dc upstream.

Return an error rather than memcpy()ing beyond the end of the buffer.
Internal callers use appropriate sizes, but digitv_i2c_xfer may not.
Signed-off-by: Alyssa Milburn <amilburn@zall.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>