iio: accel: sca3000: memory corruption in sca3000_read_first_n_hw_rb()

commit eda7d0f38aaf50dbb2a2de15e8db386c4f6f65fc upstream.

"num_read" is in byte units but we are write u16s so we end up write
twice as much as intended.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc drivers/staging/iio/accel/sca3000_ring.c
Simple merge