Add .gitignore to iomux directory
Add .gitignore to iomux directory

Change-Id: Ibefd48580f1b67ba618e2e23b8a98697e5ba009a

shashidharatd/garden-linux,savaki/garden,cloudfoundry-incubator/garden,tsaleh/garden,cloudfoundry-incubator/garden,shashidharatd/garden-linux,shashidharatd/garden-linux,tangfeixiong/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden-linux,savaki/garden,tangfeixiong/garden,cloudfoundry-incubator/garden-linux,tsaleh/garden,cloudfoundry-incubator/garden-linux