build fix: remove unused variables in usb_api_patch.c

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
add scripts/checkpatch.pl

currently developers should manually add this check with this command:
ln -s ../../scripts/pre-commit.sh .git/hooks/pre-commit

to do it automatically we need to add this command to autogen.sh or
what ever build system which we will use.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Merge pull request #10 from olerem/buildfixes

Build fixes - remove unused variables; add a pre-commit hook for people who wish to use it!

Thanks!