common: Convert the U-Boot commands to LG-arrays

This patch converts the old method of creating a list of command
onto the new LG-arrays code. The old u_boot_cmd section is converted
to new u_boot_list_cmd subsection and LG-array macros used as needed.

Minor adjustments had to be made to the common code to work with the
LG-array macros, mostly the fixup_cmdtable() calls are now passed the
ll_entry_start and ll_entry_count instead of linker-generated symbols.

The command.c had to be adjusted as well so it would use the newly
introduced LG-array API instead of directly using linker-generated
symbols.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/arm/imx-common/cmd_bmode.c b/arch/arm/imx-common/cmd_bmode.c
index 02fe72e..ddc14b0 100644
--- a/arch/arm/imx-common/cmd_bmode.c
+++ b/arch/arm/imx-common/cmd_bmode.c
@@ -24,6 +24,7 @@
 #include <asm/io.h>
 #include <asm/imx-common/boot_mode.h>
 #include <malloc.h>
+#include <command.h>
 
 static const struct boot_mode *modes[2];
 
@@ -103,9 +104,11 @@
 	int size;
 	char *dest;
 
-	if (__u_boot_cmd_bmode.usage) {
-		free(__u_boot_cmd_bmode.usage);
-		__u_boot_cmd_bmode.usage = NULL;
+	cmd_tbl_t *entry = ll_entry_get(cmd_tbl_t, bmode, cmd);
+
+	if (entry->usage) {
+		free(entry->usage);
+		entry->usage = NULL;
 	}
 
 	modes[0] = p;
@@ -114,6 +117,6 @@
 	dest = malloc(size);
 	if (dest) {
 		create_usage(dest);
-		__u_boot_cmd_bmode.usage = dest;
+		entry->usage = dest;
 	}
 }