mtd: spi-nor-core: Fix typo in documentation

This line should come before the docs for the next function.

Fixes: 7aeedac0 ("mtd: spi: Port SPI NOR framework from Linux")

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>