Fix IOCTL calls returning the wrong value

In some cases, the IOCTL functions didn't update the return value
variable so the wrong value was returned from the IOCTL calls.

Change-Id: I56529f8fb03cec52dbc555d5ed3d4e68e4bfab70
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>