dm: mmc: Allow disabling driver model in SPL

At present if U-Boot proper uses driver model for MMC, then SPL has to
also. While this is desirable, it places a significant barrier to moving
to driver model in some cases. For example, with a space-constrained SPL
it may be necessary to enable CONFIG_SPL_OF_PLATDATA which involves
adjusting some drivers.

Add new SPL versions of the options for DM_MMC, DM_MMC_OPS and BLK. By
default these follow their non-SPL versions, but this can be changed by
boards which need it.

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

drivers/block/Kconfig

@@ -10,6 +10,18 @@ config BLK
 	  be partitioned into several areas, called 'partitions' in U-Boot.
 	  A filesystem can be placed in each partition.
 
+config SPL_BLK
+	bool "Support block devices in SPL"
+	depends on SPL_DM && BLK
+	default y
+	help
+	  Enable support for block devices, such as SCSI, MMC and USB
+	  flash sticks. These provide a block-level interface which permits
+	  reading, writing and (in some cases) erasing blocks. Block
+	  devices often have a partition table which allows the device to
+	  be partitioned into several areas, called 'partitions' in U-Boot.
+	  A filesystem can be placed in each partition.
+
 config BLOCK_CACHE
 	bool "Use block device cache"
 	default n

drivers/block/Makefile

@@ -5,9 +5,9 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_BLK) += blk-uclass.o
+obj-$(CONFIG_$(SPL_)BLK) += blk-uclass.o
 
-ifndef CONFIG_BLK
+ifndef CONFIG_$(SPL_)BLK
 obj-y += blk_legacy.o
 endif