ChibiOS: add support for HID Programmable Buttons (#15787)

* ChibiOS: add support for HID Programmable Buttons

Fixes #15596

* Enable SHARED_ENDPOINT when PROGRAMMABLE_BUTTON is enabled

The Programmable Button driver expects the shared EP to be enabled.
So enforce this invariant.

tmk_core/protocol.mk

@@ -28,6 +28,11 @@ ifeq ($(strip $(EXTRAKEY_ENABLE)), yes)
     SHARED_EP_ENABLE = yes
 endif
 
+ifeq ($(strip $(PROGRAMMABLE_BUTTON_ENABLE)), yes)
+    TMK_COMMON_DEFS += -DPROGRAMMABLE_BUTTON_ENABLE
+    SHARED_EP_ENABLE = yes
+endif
+
 ifeq ($(strip $(RAW_ENABLE)), yes)
     TMK_COMMON_DEFS += -DRAW_ENABLE
 endif