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/README b/README
index ddad5ee..85d40e7 100644
--- a/README
+++ b/README
@@ -1081,7 +1081,7 @@
 				       disk/part_efi.c
 		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
 
-		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
+		If IDE or SCSI support is enabled (CONFIG_IDE or
 		CONFIG_SCSI) you must configure support for at
 		least one non-MTD partition type as well.