mtd: Introduce CONFIG_MTD_DEVICE to select compilation of mtdcore.o

This new define enables mtdcore.c compilation and with this we can
select the MTD device infrastructure needed for the reworked mtdparts
command.

We now have the 2 MTD infrastructure defines, CONFIG_MTD_DEVICE and
CONFIG_MTD_PARTITIONS. CONFIG_MTD_DEVICE is needed (as explained above)
for the "mtdparts" command and CONFIG_MTD_PARTITIONS is needed for UBI.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Scott Wood <scottwood@freescale.com>

README

@@ -1846,6 +1846,17 @@ The following options need to be configured:
 		These options enable and control the auto-update feature;
 		for a more detailed description refer to doc/README.update.
 
+- MTD Support (mtdparts command, UBI support)
+		CONFIG_MTD_DEVICE
+
+		Adds the MTD device infrastructure from the Linux kernel.
+		Needed for mtdparts command support.
+
+		CONFIG_MTD_PARTITIONS
+
+		Adds the MTD partitioning infrastructure from the Linux
+		kernel. Needed for UBI support.
+
 Legacy uImage format:
 
   Arg	Where			When

drivers/mtd/Makefile

@@ -25,7 +25,8 @@ include $(TOPDIR)/config.mk
 
 LIB	:= $(obj)libmtd.a
 
-COBJS-$(CONFIG_MTD_PARTITIONS) += mtdcore.o mtdpart.o
+COBJS-$(CONFIG_MTD_DEVICE) += mtdcore.o
+COBJS-$(CONFIG_MTD_PARTITIONS) += mtdpart.o
 COBJS-$(CONFIG_MTD_CONCAT) += mtdconcat.o
 COBJS-$(CONFIG_HAS_DATAFLASH) += at45.o
 COBJS-$(CONFIG_FLASH_CFI_DRIVER) += cfi_flash.o

drivers/mtd/nand/nand.c

@@ -57,7 +57,7 @@ static void nand_init_chip(struct mtd_info *mtd, struct nand_chip *nand,
 			else
 				mtd->name += gd->reloc_off;
 
-#ifdef CONFIG_MTD_PARTITIONS
+#ifdef CONFIG_MTD_DEVICE
 			/*
 			 * Add MTD device so that we can reference it later
 			 * via the mtdcore infrastructure (e.g. ubi).

drivers/mtd/onenand/onenand_uboot.c

@@ -43,7 +43,7 @@ void onenand_init(void)
 	puts("OneNAND: ");
 	print_size(onenand_mtd.size, "\n");
 
-#ifdef CONFIG_MTD_PARTITIONS
+#ifdef CONFIG_MTD_DEVICE
 	/*
 	 * Add MTD device so that we can reference it later
 	 * via the mtdcore infrastructure (e.g. ubi).