mtd: spi-nor: core: Call spi_nor_post_sfdp_fixups() only when SFDP is defined

spi_nor_post_sfdp_fixups() was called even when there were no SFDP
tables defined. late_init() should be instead used for flashes that
do not define SFDP tables.

Use spi_nor_post_sfdp_fixups() just to fix SFDP data. post_sfdp()
hook is as of now used just by s28hs512t, mt35xu512aba, and both
support SFDP, there's no functional change with this patch.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/20211207140254.87681-5-tudor.ambarus@microchip.com