gitconfig: Improve commit-msg hook

gitconfig: Improve commit-msg hook

There was some corner case where commit-msg failed. Update to
latest upstream version.

Change-Id: I822d6c3f64728de7356401465e00575ac5af8196
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/798
Tested-by: build bot (Jenkins)
Reviewed-by: Bernhard Urban <lewurm@gmail.com>
Reviewed-by: Rudolf Marek <r.marek@assembler.cz>