efi_loader: catch misspelled bootefi subcommand

If 'bootefi hello' or 'bootefi selftest' can be executed depends on the
configuration.

If an invalid non-numeric 1st argument is passed to bootefi, e.g.
'bootefi hola', this string is converted to 0 and U-Boot jumps to
this typically invalid address.

With the patch the online help is shown instead.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

cmd/bootefi.c

@@ -373,6 +373,9 @@ static int do_bootefi(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 		saddr = argv[1];
 
 		addr = simple_strtoul(saddr, NULL, 16);
+		/* Check that a numeric value was passed */
+		if (!addr && *saddr != '0')
+			return CMD_RET_USAGE;
 
 		if (argc > 2) {
 			sfdt = argv[2];