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/common/exports.c b/common/exports.c
index 18af38a..6253b55 100644
--- a/common/exports.c
+++ b/common/exports.c
@@ -1,4 +1,5 @@
 #include <common.h>
+#include <command.h>
 #include <exports.h>
 #include <malloc.h>
 #include <spi.h>