treewide: Make arch-specific bootm code depend on BOOTM

Allow these functions to be compiled in when CONFIG_BOOTM is enabled,
even if CONFIG_CMD_BOOTM is not.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Angelo Dureghello <angelo@kernel-space.org>
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index b1bcd37..b20a467 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -31,7 +31,7 @@
 obj-$(CONFIG_CPU_V7M) += cmd_boot.o
 obj-$(CONFIG_OF_LIBFDT) += bootm-fdt.o
 obj-$(CONFIG_CMD_BOOTI) += bootm.o image.o
-obj-$(CONFIG_CMD_BOOTM) += bootm.o
+obj-$(CONFIG_BOOTM) += bootm.o
 obj-$(CONFIG_CMD_BOOTZ) += bootm.o zimage.o
 else
 obj-$(CONFIG_$(SPL_TPL_)FRAMEWORK) += spl.o