fbmem: return -EFAULT on copy_to_user() failure

copy_to_user() returns the number of bytes remaining to be copied.
put_user() returns -EFAULT on error.

This function ORs a bunch of stuff together and returns jumbled non-zero
values on error.  It should return -EFAULT.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>