zephyr/Kconfig: deprecation of pin configuration

Added note of deprecation of hardware properties of
the gpio-pin used for triggering the recovery DFU modes.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index c67d9e3..c61c6b7 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -435,14 +435,14 @@
 if BOOT_USB_DFU_GPIO
 
 config BOOT_USB_DFU_DETECT_PORT
-	string "GPIO device to trigger USB DFU mode"
+	string "GPIO device to trigger USB DFU mode (DEPRECATED)"
 	default GPIO_0 if SOC_FAMILY_NRF
 	help
 	  Zephyr GPIO device that contains the pin used to trigger
 	  USB DFU.
 
 config BOOT_USB_DFU_DETECT_PIN
-	int "Pin to trigger USB DFU mode"
+	int "Pin to trigger USB DFU mode (DEPRECATED)"
 	default 6 if BOARD_NRF9160DK_NRF9160
 	default 11 if BOARD_NRF52840DK_NRF52840
 	default 13 if BOARD_NRF52DK_NRF52832
@@ -452,7 +452,7 @@
 	  Pin on the DFU detect port that triggers DFU mode.
 
 config BOOT_USB_DFU_DETECT_PIN_VAL
-	int "USB DFU detect pin trigger value"
+	int "USB DFU detect pin trigger value (DEPRECATED)"
 	default 0
 	range 0 1
 	help