mtd: rawnand: ingenic: fix empty stub helper definitions

A few functions provide an empty interface definition when
CONFIG_MTD_NAND_INGENIC_ECC is disabled, but they are accidentally
defined as global functions in the header:

drivers/mtd/nand/raw/ingenic/ingenic_ecc.h:39:5: error: no previous prototype for 'ingenic_ecc_calculate'
drivers/mtd/nand/raw/ingenic/ingenic_ecc.h:46:5: error: no previous prototype for 'ingenic_ecc_correct'
drivers/mtd/nand/raw/ingenic/ingenic_ecc.h:53:6: error: no previous prototype for 'ingenic_ecc_release'
drivers/mtd/nand/raw/ingenic/ingenic_ecc.h:57:21: error: no previous prototype for 'of_ingenic_ecc_get'

Turn them into 'static inline' definitions instead.

Fixes: 15de8c6e

 ("mtd: rawnand: ingenic: Separate top-level and SoC specific code")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230516202133.559488-1-arnd@kernel.org