.gitignore: ignore vim swap files
.gitignore: ignore vim swap files

Previous to this commit, `git status` shows vim swap files (*.swp) as
untracked files, which can lead to being added accidentally in commits.

This commit makes git to ignore those files, reducing the changes of add
them by accident.

Signed-off-by: Simental Magana, Marcos <5982b30768aab49bc152fe3056e26fec2435452f@intel.com>

markdryan/ciao,01org/ciao,mrkz/ciao,rbradford/ciao,erick0z/ciao,01org/ciao,mrkz/ciao,obedmr/ciao,markdryan/ciao,erick0z/ciao,kaccardi/ciao,rbradford/ciao,matthewrsj/ciao,mcastelino/ciao,kaccardi/ciao,tpepper/ciao,mcastelino/ciao,mcastelino/ciao,mrkz/ciao,wcwxyz/ciao,matthewrsj/ciao,matthewrsj/ciao,tpepper/ciao,erick0z/ciao,wcwxyz/ciao,ciao-project/ciao,ciao-project/ciao,obedmr/ciao,tpepper/ciao,wcwxyz/ciao,obedmr/ciao