Input: serio_raw - signal EFAULT even if read/write partially succeeds

Input: serio_raw - signal EFAULT even if read/write partially succeeds

When copy_to/from_user fails in the middle of transfer we should not
report to the user that read/write partially succeeded but rather
report -EFAULT right away, so that application will know that it got
its buffers all wrong.

If application messed up its buffers we can't trust the data fetched
from userspace and successfully written to the device or if data read
from the device and transferred to userspace ended up where application
expected it to end.

If serio_write() fails we still going to report partial writes if failure
happens in the middle of the transfer.

This is basically a revert of 7a0a27d2ce38aee19a31fee8c12095f586eed393
and 4fa0771138d0b56fe59ab8ab3b1ce9e594484362.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>