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/include/exports.h b/include/exports.h
index cbd16fc..85f9a7a 100644
--- a/include/exports.h
+++ b/include/exports.h
@@ -11,6 +11,7 @@
 
 #include <irq_func.h>
 
+struct cmd_tbl;
 struct spi_slave;
 
 /* Set up the jump table for use by the API */