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/examples/standalone/stubs.c b/examples/standalone/stubs.c
index 0827bde..5fb4604 100644
--- a/examples/standalone/stubs.c
+++ b/examples/standalone/stubs.c
@@ -2,6 +2,8 @@
 #include <exports.h>
 #include <linux/compiler.h>
 
+struct cmd_tbl;
+
 #define FO(x) offsetof(struct jt_funcs, x)
 
 #if defined(CONFIG_X86)