mtd, nand: Move common functions from cmd_nand.c to common place

Move common functions from cmd_nand.c (for calculating offset
and size from cmdline paramter) to common place, so they could
used from other commands which use mtd partitions.

For onenand the arg_off_size() is left in common/cmd_onenand.c.
It should use now the common arg_off() function, but as I could
not test onenand I let it there ...

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Scott Wood <scottwood@freescale.com>
Reviewed-by: Jagannadh Teki <jteki@openedev.com>
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 5467a95..a623f4c 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -5,8 +5,8 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-ifneq (,$(findstring y,$(CONFIG_MTD_DEVICE)$(CONFIG_CMD_NAND)$(CONFIG_CMD_ONENAND)))
-obj-y += mtdcore.o
+ifneq (,$(findstring y,$(CONFIG_MTD_DEVICE)$(CONFIG_CMD_NAND)$(CONFIG_CMD_ONENAND)$(CONFIG_CMD_SF)))
+obj-y += mtdcore.o mtd_uboot.o
 endif
 obj-$(CONFIG_MTD_PARTITIONS) += mtdpart.o
 obj-$(CONFIG_MTD_CONCAT) += mtdconcat.o