mtd: nand: fix error handling in nand_prog_page_op() #2

On success nand_exec_prog_page_op() returns the NAND status byte, but on
failure it returns a negative error code. nand_prog_page_op() interprets
the return value as NAND status byte without error checking.  This means
a failure in nand_exec_prog_page_op() can go through unnoticed.

The straight forward fix would be to add the missing error checking. To
clean the code a bit we can move the nand status check to
nand_prog_page_op().  This way we can get rid of the overloaded return
value from nand_exec_prog_page_op() and return a plain error code which
is less error prone.

nand_exec_prog_page_op() is only called from one other place and in this
call the 'prog' parameter is false in which case the nand status check
is skipped, so it's correct to not add the NAND status check there.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210205142725.13225-2-s.hauer@pengutronix.de