mtd: nand: add out label in rfc_from4

This has been forgotten in commit f5bbdacc

 ("[MTD] NAND Modularize
read function") and nobody compiled the driver.

Signed-off-by: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Joern Engel <joern@wh.fh-wedel.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>