cmd: fix lsblk command

Add missing includes.
Add CMD_LSBLK to sandbox_defconfig.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/cmd/lsblk.c b/cmd/lsblk.c
index ece8bbf..653dffc 100644
--- a/cmd/lsblk.c
+++ b/cmd/lsblk.c
@@ -5,6 +5,8 @@
  */
 
 #include <common.h>
+#include <blk.h>
+#include <command.h>
 #include <dm.h>
 
 static int do_lsblk(struct cmd_tbl *cmdtp, int flag, int argc, char * const argv[])