mtd: spi-nand: Import Toshiba SPI-NAND support

Linux has good support for Toshiba SPI-NAND, so lets import it.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Tested-by: Luka Kovacic <luka.kovacic@sartura.hr>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>