scripts/get_abi.pl: fix parse issues with some files

A few files are failing to parse:

	Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
	Documentation/ABI/testing/sysfs-class-pktcdvd
	Documentation/ABI/testing/sysfs-bus-nfit

On all three files, the problem is that there is a ":" character
at the initial file description.

Improve the parse in order to handle those special cases.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/get_abi.pl

@@ -87,7 +87,7 @@ sub parse_abi {
 					# New "tag" is actually part of
 					# description. Don't consider it a tag
 					$new_tag = "";
-				} else {
+				} elsif ($tag ne "") {
 					parse_error($file, $ln, "tag '$tag' is invalid", $_);
 				}
 			}
@@ -110,7 +110,7 @@ sub parse_abi {
 				next;
 			}
 
-			if ($new_tag) {
+			if ($tag ne "" && $new_tag) {
 				$tag = $new_tag;
 
 				if ($new_what) {