mtd: spinand: winbond: Add comment about naming

Make the link between the core macros and the datasheet.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: miquelraynal

drivers/mtd/nand/spi/winbond.c

@@ -18,6 +18,11 @@
 
 #define W25N04KV_STATUS_ECC_5_8_BITFLIPS	(3 << 4)
 
+/*
+ * "X2" in the core is equivalent to "dual output" in the datasheets,
+ * "X4" in the core is equivalent to "quad output" in the datasheets.
+ */
+
 static SPINAND_OP_VARIANTS(read_cache_dtr_variants,
 		SPINAND_PAGE_READ_FROM_CACHE_QUADIO_OP(0, 2, NULL, 0),
 		SPINAND_PAGE_READ_FROM_CACHE_X4_OP(0, 1, NULL, 0),