misc: xilinx_sdfec: Return -EFAULT if copy_from_user() fails

The copy_from_user() function returns the number of bytes remaining to
be copied but we want to return -EFAULT to the user.

Fixes: 20ec628e ("misc: xilinx_sdfec: Add ability to configure LDPC")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Dragan Cvetic <dragan.cvetic@xilinx.com>
Link: https://lore.kernel.org/r/20190822083105.GI3964@kadam


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>