blk: Rename HAVE_BLOCK_DEVICE

This option is fact really related to SPL. For U-Boot proper we always use
driver model for block devices, so CONFIG_BLK is enabled if block devices
are in use.

It is only for SPL that we have two cases:

- SPL_BLK is enabled, in which case we use driver model and blk-uclass.c
- SPL_BLK is not enabled, in which case (if we need block devices) we must
  use blk_legacy.c

Rename the symbol to SPL_LEGACY_BLOCK to make this clear. This is
different enough from BLK and SPL_BLK that there should be no confusion.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/blk.h

@@ -23,7 +23,7 @@ struct udevice;
 
 static inline bool blk_enabled(void)
 {
-	return CONFIG_IS_ENABLED(BLK) || IS_ENABLED(CONFIG_HAVE_BLOCK_DEVICE);
+	return CONFIG_IS_ENABLED(BLK) || IS_ENABLED(CONFIG_SPL_LEGACY_BLOCK);
 }
 
 /* Interface types: */