mtd: spi-nor: Improve Kconfig help text for SPI_FSL_QUADSPI

The current "We only connect the NOR to this controller now." text
is not very clear, so explain it better by saying that generic SPI
is not supported by SPI_FSL_QUADSPI and only SPI NOR is.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/spi-nor/Kconfig

@@ -26,7 +26,8 @@ config SPI_FSL_QUADSPI
 	depends on ARCH_MXC
 	help
 	  This enables support for the Quad SPI controller in master mode.
-	  We only connect the NOR to this controller now.
+	  This controller does not support generic SPI. It only supports
+	  SPI NOR.
 
 config SPI_NXP_SPIFI
 	tristate "NXP SPI Flash Interface (SPIFI)"