command: Remove the cmd_tbl_t typedef

We should not use typedefs in U-Boot. They cannot be used as forward
declarations which means that header files must include the full header to
access them.

Drop the typedef and rename the struct to remove the _s suffix which is
now not useful.

This requires quite a few header-file additions.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/exit.c b/cmd/exit.c
index f40d068..7bf241e 100644
--- a/cmd/exit.c
+++ b/cmd/exit.c
@@ -7,7 +7,8 @@
 #include <common.h>
 #include <command.h>
 
-static int do_exit(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+static int do_exit(struct cmd_tbl *cmdtp, int flag, int argc,
+		   char *const argv[])
 {
 	int r;