feat(app-crypt/sbsigntool) update to latest upstream patches

This fixes a bug in sbsigntool that would cause newer UEFI firmware
images to fail the signature check of the booting binary.  This would
always show up on any firmware that supported multi-key signatures of
binaries.
Merge pull request #56 from gregkh/app-crypt

feat(app-crypt/sbsigntool) update to latest upstream patches