mtd: spi-nor: sst: fix BPn bits for the SST25VF064C

This flash part actually has 4 block protection bits.

Please note, that this patch is just based on information of the
datasheet of the datasheet and wasn't tested.

Fixes: 3e0930f ("mtd: spi-nor: Rework the disabling of block write protection")
Reported-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201203162959.29589-2-michael@walle.cc

drivers/mtd/spi-nor/sst.c

@@ -18,7 +18,8 @@ static const struct flash_info sst_parts[] = {
 			      SECT_4K | SST_WRITE) },
 	{ "sst25vf032b", INFO(0xbf254a, 0, 64 * 1024, 64,
 			      SECT_4K | SST_WRITE) },
-	{ "sst25vf064c", INFO(0xbf254b, 0, 64 * 1024, 128, SECT_4K) },
+	{ "sst25vf064c", INFO(0xbf254b, 0, 64 * 1024, 128,
+			      SECT_4K | SPI_NOR_4BIT_BP) },
 	{ "sst25wf512",  INFO(0xbf2501, 0, 64 * 1024,  1,
 			      SECT_4K | SST_WRITE) },
 	{ "sst25wf010",  INFO(0xbf2502, 0, 64 * 1024,  2,