mtd: m25p80: replace leftover "nor-jedec" with "spi-nor" in comments

I overlooked a few comments in commit 8947e396 ("Documentation: dt:
mtd: replace "nor-jedec" binding with "jedec, spi-nor""). Fix these up
now.

Suggested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>