linux-phytec-fsl

mtd: nand: remove unnecessary 'extern' from function declarations

'extern' is not necessary for function declarations. To prevent
people from adding the keyword to new declarations remove the
existing ones.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>