mtd: spi-nor: core: Update flash's current address mode when changing address mode

The bug was obswerved while reading code. There are not many users of
addr_mode_nbytes. Anyway, we should update the flash's current address
mode when changing the address mode, fix it. We don't care for now about
the set_4byte_addr_mode(nor, false) from spi_nor_restore(), as it is
used at driver remove and shutdown.

Fixes: d7931a21

 ("mtd: spi-nor: core: Track flash's internal address mode")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230331074606.3559258-9-tudor.ambarus@linaro.org
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>