blk: Make use of CONFIG_HAVE_BLOCK_DEVICE more

When we do not have CONFIG_BLK (or SPL/TPL) enabled there are very few
cases where we need the blk_legacy code linked in. To catch these, build
when we have CONFIG_HAVE_BLOCK_DEVICE set.  In addition, we only need
cmd/blk_common.o to be linked in when we have CONFIG_HAVE_BLOCK_DEVICE
set, so make use of that directly.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Makefile b/cmd/Makefile
index 2d723ea..f823d16 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -15,7 +15,7 @@
 obj-$(CONFIG_CMD_AB_SELECT) += ab_select.o
 obj-$(CONFIG_CMD_ADC) += adc.o
 obj-$(CONFIG_CMD_ARMFLASH) += armflash.o
-obj-y += blk_common.o
+obj-$(CONFIG_HAVE_BLOCK_DEVICE) += blk_common.o
 obj-$(CONFIG_CMD_SOURCE) += source.o
 obj-$(CONFIG_CMD_BCB) += bcb.o
 obj-$(CONFIG_CMD_BDI) += bdinfo.o