zephyr: add Laird Connectivity BL5340 recovery pin

Signed-off-by: Jamie McCrae <jamie.mccrae@lairdconnect.com>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 2e7ac39..932110d 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -404,6 +404,7 @@
 	default 11 if BOARD_NRF52840DK_NRF52840
 	default 13 if BOARD_NRF52DK_NRF52832
 	default 23 if BOARD_NRF5340_DK_NRF5340_CPUAPP || BOARD_NRF5340_DK_NRF5340_CPUAPPNS
+	default 43 if BOARD_BL5340_DVK_CPUAPP || BOARD_BL5340_DVK_CPUAPPNS
 	help
 	  Pin on the DFU detect port that triggers DFU mode.