drivers: introduce mtdblock abstraction

MTD block - abstraction over MTD subsystem, allowing
to read and write in blocks using BLK UCLASS.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index c2fc80b..10d575e 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -26,6 +26,7 @@
 obj-y += spi/
 obj-$(CONFIG_MTD_UBI) += ubi/
 obj-$(CONFIG_NVMXIP) += nvmxip/
+obj-$(CONFIG_MTD_BLOCK) += mtdblock.o
 
 #SPL/TPL build
 else