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>