mtd: nand: gpio: improve comments about GPIO assisted operation

The drivers/mtd/nand/gpio.c driver does not GPIO bitbang the complete
NAND protocol, but instead is GPIO _assisted_ -- a memory mapped interface
communicates commands and data, and only few control signals are connected
to GPIO pins.

Expand comments in the driver source and in the Kconfig description to
better reflect the very nature of the driver.  The previous text could be
mistaken for complete GPIO bitbanging.

Signed-off-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/Kconfig

@@ -75,10 +75,12 @@ config MTD_NAND_DENALI_SCRATCH_REG_ADDR
           boards, the scratch register is at 0xFF108018.
 
 config MTD_NAND_GPIO
-	tristate "GPIO NAND Flash driver"
+	tristate "GPIO assisted NAND Flash driver"
 	depends on GPIOLIB
 	help
-	  This enables a GPIO based NAND flash driver.
+	  This enables a NAND flash driver where control signals are
+	  connected to GPIO pins, and commands and data are communicated
+	  via a memory mapped interface.
 
 config MTD_NAND_AMS_DELTA
 	tristate "NAND Flash device on Amstrad E3"

drivers/mtd/nand/gpio.c

@@ -8,7 +8,9 @@
  *
  * © 2004 Simtec Electronics
  *
- * Device driver for NAND connected via GPIO
+ * Device driver for NAND flash that uses a memory mapped interface to
+ * read/write the NAND commands and data, and GPIO pins for control signals
+ * (the DT binding refers to this as "GPIO assisted NAND flash")
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as