blk: Drop reference to DM_SPL

The intent here is to only allow SPL_LEGACY_BLK if !SPL_DM - i.e. that
when driver model is enabled in SPL, legacy block cannot be used.

However this combination is used by about 240 boards, so we cannot
disallow it, at least not yet.

So just drop the condition.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index b897cf1..6ad1888 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -13,7 +13,7 @@
 
 config SPL_LEGACY_BLOCK
 	bool # "Enable Legacy Block Device"
-	depends on SPL && !DM_SPL
+	depends on SPL
 	default y if SPL_MMC || SPL_USB_STORAGE || SCSI || NVME || IDE
 	default y if SPL_AHCI_PCI
 	help