mtd: spi: spi-nor-core: Add SST vendor specific SFDP parser

JESD216 allow vendors to define their own SFDP tables.

Add SST SFDP parser. The vendor table is allocated using resource-managed
kmalloc - the table will be freed on driver detach. It will be accessible
by getting the UCLASS_SPI_FLASH's private data.

The SST's SFDP table is particularly of interest because contains
pre-programmed globally unique EUI-48 and EUI-64 identifiers.

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