tests/driver_hih6130: simplified Makefile

tests/driver_hih6130/Makefile

@@ -6,17 +6,12 @@ FEATURES_REQUIRED = periph_i2c
 USEMODULE += hih6130
 USEMODULE += xtimer
 
-ifneq (,$(TEST_HIH6130_I2C))
-  CFLAGS += -DTEST_HIH6130_I2C=$(TEST_HIH6130_I2C)
-else
-  # set arbitrary default
-  CFLAGS += -DTEST_HIH6130_I2C=I2C_0
-endif
-ifneq (,$(TEST_HIH6130_ADDR))
-  CFLAGS += -DTEST_HIH6130_ADDR=$(TEST_HIH6130_ADDR)
-else
-  # factory default address
-  CFLAGS += -DTEST_HIH6130_ADDR=0x27
-endif
+# set default device parameters in case they are undefined
+TEST_HIH6130_I2C  ?= I2C_0
+TEST_HIH6130_ADDR ?= 0x27
+
+# export parameters
+CFLAGS += -DTEST_HIH6130_I2C=$(TEST_HIH6130_I2C)
+CFLAGS += -DTEST_HIH6130_ADDR=$(TEST_HIH6130_ADDR)
 
 include $(RIOTBASE)/Makefile.include