mtd: spi-nor: Check all the bits written, not just the BP ones

Check that all the bits written in the write_sr_and_check() method
match the status_new received value. Failing to write the other bits
is dangerous too, extend the check.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>