Make sure that argv[] argument pointers are not modified.

The hush shell dynamically allocates (and re-allocates) memory for the
argument strings in the "char *argv[]" argument vector passed to
commands.  Any code that modifies these pointers will cause serious
corruption of the malloc data structures and crash U-Boot, so make
sure the compiler can check that no such modifications are being done
by changing the code into "char * const argv[]".

This modification is the result of debugging a strange crash caused
after adding a new command, which used the following argument
processing code which has been working perfectly fine in all Unix
systems since version 6 - but not so in U-Boot:

int main (int argc, char **argv)
{
	while (--argc > 0 && **++argv == '-') {
/* ====> */	while (*++*argv) {
			switch (**argv) {
			case 'd':
				debug++;
				break;
			...
			default:
				usage ();
			}
		}
	}
	...
}

The line marked "====>" will corrupt the malloc data structures and
usually cause U-Boot to crash when the next command gets executed by
the shell.  With the modification, the compiler will prevent this with
an
	error: increment of read-only location '*argv'

N.B.: The code above can be trivially rewritten like this:

	while (--argc > 0 && **++argv == '-') {
		char *arg = *argv;
		while (*++arg) {
			switch (*arg) {
			...

Signed-off-by: Wolfgang Denk <wd@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>

common/cmd_test.c

@@ -24,9 +24,9 @@
 #include <common.h>
 #include <command.h>
 
-int do_test(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_test(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	char **ap;
+	char * const *ap;
 	int left, adv, expr, last_expr, neg, last_cmp;
 
 	/* args? */
@@ -150,7 +150,7 @@ U_BOOT_CMD(
 	"[args..]"
 );
 
-int do_false(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_false(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	return 1;
 }
@@ -161,7 +161,7 @@ U_BOOT_CMD(
 	NULL
 );
 
-int do_true(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_true(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	return 0;
 }