mtd: spi-nor-ids: Add Spansion s25fs512s flash entry

Spansion "s25fs512s" flash is incorrectly decoded as "s25fl512s" on
various platforms as former is not present. Add the entry.

Linux already has both the flashes present. A snippet below:
{ "s25fl512s",  INFO6(0x010220, 0x4d0080, 256 * 1024, 256...},
{ "s25fs512s",  INFO6(0x010220, 0x4d0081, 256 * 1024, 256...},

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>