sim/ppc: Fix check for --sysroot= option

Fixes an error reported by Tristan and which can be evidenced by
doing:

        % powerpc-elf-gdb
        (gdb) target sim --sysroot=var
        Invalid option: --sysroot=/var
        [...]

sim/ppc/ChangeLog:

        * psim.c (psim_options): Fix length of comparison when checking
        for --sysroot= option.

sim/ppc/ChangeLog

@@ -1,3 +1,8 @@
+2011-06-09  Joel Brobecker  <brobecker@adacore.com>
+
+	* psim.c (psim_options): Fix length of comparison when checking
+	for --sysroot= option.
+
 2011-06-08  Joel Brobecker  <brobecker@adacore.com>
 
 	* psim.c (psim_options): Add option that cause the error

sim/ppc/psim.c

@@ -359,7 +359,7 @@ psim_options(device *root,
 	else if (strcmp (argv[argp], "--help") == 0)
 	  psim_usage (0, 1);
 	else if (strncmp (argv[argp], "--sysroot=",
-			  sizeof ("--sysroot=")) == 0)
+			  sizeof ("--sysroot=") - 1) == 0)
 	  /* Ignore this option.  */
 	  p = argv[argp] + strlen(argv[argp]) - 1;
 	else if (strcmp (argv[argp], "--version") == 0)