mtd: spi-nor: fix spi_nor_spimem_setup_op() call in spi_nor_erase_{sector,chip}()

For erase operations, reg_proto must be used as indicated in
struct spi_nor description in spi-nor.h.

This issue was found when DT property spi-tx-bus-width is set to 4.
In this case the spi_mem_op->addr.buswidth is set to 4 for erase command
which is not correct.

Tested on stm32mp157c-ev1 board with mx66l51235f spi-nor.

Fixes: 0e30f472

 ("mtd: spi-nor: add support for DTR protocol")
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
[ta: use nor->reg_proto in spi_nor_controller_ops_erase()]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/20220629133013.3382393-1-patrice.chotard@foss.st.com