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/fs/fat/fat.c b/fs/fat/fat.c
index 5654003..a71bad1 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -1250,7 +1250,7 @@
 		return 1;
 	}
 
-#if defined(CONFIG_CMD_IDE) || \
+#if defined(CONFIG_IDE) || \
     defined(CONFIG_CMD_SATA) || \
     defined(CONFIG_SCSI) || \
     defined(CONFIG_CMD_USB) || \