drivers: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 6e203a3..a78a724 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -8,36 +8,14 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
 #CFLAGS += -DDEBUG
 
-LIB	= $(obj)libhwmon.o
-
-COBJS-$(CONFIG_DTT_ADM1021) += adm1021.o
-COBJS-$(CONFIG_DTT_ADT7460) += adt7460.o
-COBJS-$(CONFIG_DTT_DS1621) += ds1621.o
-COBJS-$(CONFIG_DTT_DS1722) += ds1722.o
-COBJS-$(CONFIG_DTT_DS1775) += ds1775.o
-COBJS-$(CONFIG_DTT_LM63) += lm63.o
-COBJS-$(CONFIG_DTT_LM73) += lm73.o
-COBJS-$(CONFIG_DTT_LM75) += lm75.o
-COBJS-$(CONFIG_DTT_LM81) += lm81.o
-
-COBJS	:= $(COBJS-y)
-SRCS	:= $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-
-all:	$(LIB)
-
-$(LIB):	$(obj).depend $(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################
+obj-$(CONFIG_DTT_ADM1021) += adm1021.o
+obj-$(CONFIG_DTT_ADT7460) += adt7460.o
+obj-$(CONFIG_DTT_DS1621) += ds1621.o
+obj-$(CONFIG_DTT_DS1722) += ds1722.o
+obj-$(CONFIG_DTT_DS1775) += ds1775.o
+obj-$(CONFIG_DTT_LM63) += lm63.o
+obj-$(CONFIG_DTT_LM73) += lm73.o
+obj-$(CONFIG_DTT_LM75) += lm75.o
+obj-$(CONFIG_DTT_LM81) += lm81.o