mtd: spi-nor: Split spi_nor_init_params()

Add functions to delimit what the chunks of code do:

static void spi_nor_init_params()
{
	spi_nor_info_init_params()
	spi_nor_manufacturer_init_params()
	spi_nor_sfdp_init_params()
}

Add descriptions to all methods.

spi_nor_init_params() becomes of type void, as all its children
return void.

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