w1: add command for onewire protocol

Add basic command for bus information and read for onewire
bus using Dallas 1-Wire protocol.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/cmd/Makefile b/cmd/Makefile
index d3815ab..9e311a7 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -146,6 +146,7 @@
 obj-$(CONFIG_CMD_XIMG) += ximg.o
 obj-$(CONFIG_CMD_YAFFS2) += yaffs2.o
 obj-$(CONFIG_CMD_SPL) += spl.o
+obj-$(CONFIG_CMD_W1) += w1.o
 obj-$(CONFIG_CMD_ZIP) += zip.o
 obj-$(CONFIG_CMD_ZFS) += zfs.o