mtd: spi-nor: core: Don't use mtd_info in the NOR's probe sequence of calls

Use NOR parameters in the probe's sequence of calls, thus
nor->params->size instead of nor->mtd.size and let the mtd_info
fields be used by the mtd calls (mtd->_erase, mtd->_read, mtd->_write).
mtd_info fields should not be used during probe because we haven't
registered mtd yet. It's safe to drop xilinx's setting of nor->mtd.size,
now that we use nor->params->size in spi_nor_set_addr_width().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/20211207140254.87681-3-tudor.ambarus@microchip.com