pgm: don't advance bp by the option haeder length twice.

At those points, we've already advanced it by the option header length,
and opt_len includes that length, so advance bp by opt_len minus the
option header length.

Fixes #1024.

Author: guyharris

print-pgm.c

@@ -674,7 +674,7 @@ pgm_print(netdissect_options *ndo,
 
 		case PGM_OPT_PATH_NLA:
 		    ND_PRINT(" PATH_NLA [%u]", opt_len);
-		    bp += opt_len;
+		    bp += opt_len - 2;
 		    opts_len -= opt_len;
 		    break;
 
@@ -716,7 +716,7 @@ pgm_print(netdissect_options *ndo,
 
 		case PGM_OPT_CR:
 		    ND_PRINT(" CR");
-		    bp += opt_len;
+		    bp += opt_len - 2;
 		    opts_len -= opt_len;
 		    break;
 
@@ -820,7 +820,7 @@ pgm_print(netdissect_options *ndo,
 
 		default:
 		    ND_PRINT(" OPT_%02X [%u] ", opt_type, opt_len);
-		    bp += opt_len;
+		    bp += opt_len - 2;
 		    opts_len -= opt_len;
 		    break;
 		}