core: Fix build config in protocol.mk (#7620)

Backports commits from tmk_keyboard

tmk_core/protocol.mk

@@ -1,56 +1,55 @@
 PROTOCOL_DIR = protocol
 
-
-ifdef PS2_MOUSE_ENABLE
+ifeq ($(strip $(PS2_MOUSE_ENABLE)), yes)
     SRC += $(PROTOCOL_DIR)/ps2_mouse.c
     OPT_DEFS += -DPS2_MOUSE_ENABLE
     OPT_DEFS += -DMOUSE_ENABLE
 endif
 
-ifdef PS2_USE_BUSYWAIT
+ifeq ($(strip $(PS2_USE_BUSYWAIT)), yes)
     SRC += protocol/ps2_busywait.c
     SRC += protocol/ps2_io_avr.c
     OPT_DEFS += -DPS2_USE_BUSYWAIT
 endif
 
-ifdef PS2_USE_INT
+ifeq ($(strip $(PS2_USE_INT)), yes)
     SRC += protocol/ps2_interrupt.c
     SRC += protocol/ps2_io_avr.c
     OPT_DEFS += -DPS2_USE_INT
 endif
 
-ifdef PS2_USE_USART
+ifeq ($(strip $(PS2_USE_USART)), yes)
     SRC += protocol/ps2_usart.c
     SRC += protocol/ps2_io_avr.c
     OPT_DEFS += -DPS2_USE_USART
 endif
 
 
-ifdef SERIAL_MOUSE_MICROSOFT_ENABLE
+ifeq ($(strip $(SERIAL_MOUSE_MICROSOFT_ENABLE)), yes)
     SRC += $(PROTOCOL_DIR)/serial_mouse_microsoft.c
     OPT_DEFS += -DSERIAL_MOUSE_ENABLE -DSERIAL_MOUSE_MICROSOFT \
                 -DMOUSE_ENABLE
 endif
 
-ifdef SERIAL_MOUSE_MOUSESYSTEMS_ENABLE
+ifeq ($(strip $(SERIAL_MOUSE_MOUSESYSTEMS_ENABLE)), yes)
     SRC += $(PROTOCOL_DIR)/serial_mouse_mousesystems.c
     OPT_DEFS += -DSERIAL_MOUSE_ENABLE -DSERIAL_MOUSE_MOUSESYSTEMS \
                 -DMOUSE_ENABLE
 endif
 
-ifdef SERIAL_MOUSE_USE_SOFT
+ifeq ($(strip $(SERIAL_MOUSE_USE_SOFT)), yes)
     SRC += $(PROTOCOL_DIR)/serial_soft.c
 endif
 
-ifdef SERIAL_MOUSE_USE_UART
+ifeq ($(strip $(SERIAL_MOUSE_USE_UART)), yes)
     SRC += $(PROTOCOL_DIR)/serial_uart.c
 endif
 
-ifdef ADB_MOUSE_ENABLE
+ifeq ($(strip $(ADB_MOUSE_ENABLE)), yes)
     OPT_DEFS += -DADB_MOUSE_ENABLE -DMOUSE_ENABLE
 endif
 
-ifdef XT_ENABLE
+ifeq ($(strip $(XT_ENABLE)), yes)
     SRC += $(PROTOCOL_DIR)/xt_interrupt.c
     OPT_DEFS += -DXT_ENABLE
 endif