Fix coccicheck warning which recommends to use memdup_user().

This patch fixes the following coccicheck warnings:

drivers/misc/xilinx_sdfec.c:652:8-15: WARNING opportunity for memdup_user
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Link: https://lore.kernel.org/r/1587524330-119776-1-git-send-email-zou_wei@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>