mtd: inftlcore: fix repeated words in comments

Delete the redundant word 'it'.

Signed-off-by: Jilin Yuan <yuanjilin@cdjrlc.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20221028134036.63000-1-yuanjilin@cdjrlc.com