Staging: panel: change asm/uaccess.h to linux/uaccess.h

This patch replaces <asm/uaccess.h> with <linux/uaccess.h> to comply with
the checkpatch.pl hint.

Signed-off-by: Takanori Suzuki <mail.tks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>