mtd: spi-nor: Use nor->params

The Flash parameters and settings are now stored in 'struct spi_nor'.
Use this instead of the stack allocated params.

Few functions stop passing pointer to params, as they can get it from
'struct spi_nor'. spi_nor_parse_sfdp() and children will keep passing
pointer to params because of the roll-back mechanism: in case the
parsing of SFDP fails, the legacy flash parameter and settings will be
restored.

Zeroing params is no longer needed because all SPI NOR users kzalloc
'struct spi_nor'.

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