[PATCH] Fix build error due to not including <linux/errno.h>

Since d9a9cdfb <linux/sysfs.h> is using
ENOSYS without including <linux/errno.h> if CONFIG_SYSFS is disabled.

Fixed by including <linux/errno.h>.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>