.gitignore: Added .o.cmd extension
.gitignore: Added .o.cmd extension

Signed-off-by: Henry Bruce <57ea958cad66de244404958c9a01f7a4ad51b29e@intel.com>

whbruce/zmraa,intel-iot-devkit/zmraa,malikabhi05/zmraa-1,jontrulson/zmraa