Blackfin arch: PM_BFIN_WAKE_GP: update help

Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>

arch/blackfin/Kconfig

@@ -1168,6 +1168,12 @@ config PM_BFIN_WAKE_GP
 	default n
 	help
 	  Enable General-Purpose Wake-Up (Voltage Regulator Power-Up)
+	  (all processors, except ADSP-BF549). This option sets
+	  the general-purpose wake-up enable (GPWE) control bit to enable
+	  wake-up upon detection of an active low signal on the /GPW (PH7) pin.
+	  On ADSP-BF549 this option enables the the same functionality on the
+	  /MRXON pin also PH7.
+
 endmenu
 
 menu "CPU Frequency scaling"