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_pci.c

@@ -471,7 +471,7 @@ pci_cfg_modify (pci_dev_t bdf, ulong addr, ulong size, ulong value, int incrflag
  *      pci modify[.b, .w, .l] bus.device.function [addr]
  *      pci write[.b, .w, .l] bus.device.function addr value
  */
-int do_pci (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_pci (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	ulong addr = 0, value = 0, size = 0;
 	pci_dev_t bdf = 0;