mtd: spi-nor: don't drop sfdp data if optional parsers fail

JESD216C states that just the Basic Flash Parameter Table is mandatory.
Already defined (or future) additional parameter headers and tables are
optional.

Don't drop already collected sfdp data in case an optional table
parser fails. In case of failing, each optional parser is responsible
to roll back to the previously known spi_nor data.

Fixes: b038e8e3 ("mtd: spi-nor: parse SFDP Sector Map Parameter Table")
Reported-by: Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Tested-by: Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>