Kconfig: Add a CONFIG_IDE option

At present IDE support is controlled by CONFIG_CMD_IDE. Add a separate
CONFIG_IDE option so that IDE support can be enabled without requiring
the 'ide' command.

Update existing users and move the ide driver into drivers/block since
it should not be in common/.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 4f68613..88adb26 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -35,7 +35,7 @@
 obj-y	+= extable.o
 obj-y	+= interrupts.o
 obj-$(CONFIG_CMD_KGDB) += kgdb.o
-obj-$(CONFIG_CMD_IDE) += ide.o
+obj-$(CONFIG_IDE) += ide.o
 obj-y	+= stack.o
 obj-y	+= time.o