dm: unify obj-$(CONFIG_DM) and obj-$(CONFIG_SPL_DM) entries

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/Makefile

+obj-$(CONFIG_$(SPL_)DM)		+= core/
+
 ifdef CONFIG_SPL_BUILD
 
 obj-$(CONFIG_SPL_CLK_SUPPORT) += clk/
-obj-$(CONFIG_SPL_DM) += core/
 obj-$(CONFIG_SPL_I2C_SUPPORT) += i2c/
 obj-$(CONFIG_SPL_GPIO_SUPPORT) += gpio/
 obj-$(CONFIG_SPL_MMC_SUPPORT) += mmc/
@@ -34,7 +35,6 @@ obj-$(CONFIG_SPL_SATA_SUPPORT) += block/
 else
 
 obj-$(CONFIG_CLK) += clk/
-obj-$(CONFIG_DM) += core/
 obj-$(CONFIG_DM_DEMO) += demo/
 obj-$(CONFIG_BIOSEMU) += bios_emulator/
 obj-y += block/