add instruction for updating the BLE firmware

doc/AP4_BLE_Firmware_Update.md

@@ -0,0 +1,31 @@
+## BLE firmware update method
+
+1. Navigating to the folder in the AmbiqSuite SDK which contains the firmware update example
+
+```bash
+# adjusting the path if neccesary
+cd AmbiqSuite_R4.5.0/AmbiqSuite_R4.5.0/boards/apollo4p_blue_kbr_evb/examples/ble/ble_firmware_update/gcc
+```
+
+2. Run the following commands, with JLink debugger attached to the device.
+```bash
+make
+
+echo 'r
+loadfile bin/ble_firmware_update.bin 0x00018000
+r
+g
+exit' > bin/flash.jlink
+
+JLinkExe -device AMA4B2KK-KBR -if swd -speed 4000 bin/flash.jlink
+```
+
+3. Reflash the device with the app, and verify the updated firmware version at device startup.
+```
+Reset Reasons: HW Power-On Reset, 
+BLE Controller Info:
+        SBL Ver:     V1
+        FW Ver:      1.22.0.0
+        Chip ID0:    0x92492492
+        Chip ID1:    0x4170383c
+```