cmd: blkls: Add blkls command

Add a command to print a list of available block device drivers,
and for each, the list of known block devices.

Signed-off-by: Niel Fourie <lusus@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 192b3b2..0ead88e 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1088,6 +1088,13 @@
 	help
 	  Load an S-Record file over serial line
 
+config CMD_LSBLK
+	depends on BLK
+	bool "lsblk - list block drivers and devices"
+	help
+	  Print list of available block device drivers, and for each, the list
+	  of known block devices.
+
 config CMD_MMC
 	bool "mmc"
 	help