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/arch/arm/mach-imx/mx6/clock.c b/arch/arm/mach-imx/mx6/clock.c
index 6a9e673..9f3d62f 100644
--- a/arch/arm/mach-imx/mx6/clock.c
+++ b/arch/arm/mach-imx/mx6/clock.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <command.h>
 #include <div64.h>
 #include <asm/io.h>
 #include <linux/errno.h>
@@ -1305,7 +1306,8 @@
 /*
  * Dump some core clockes.
  */
-int do_mx6_showclocks(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+int do_mx6_showclocks(struct cmd_tbl *cmdtp, int flag, int argc,
+		      char *const argv[])
 {
 	u32 freq;
 	freq = decode_pll(PLL_SYS, MXC_HCLK);