Driver_Motor: Add TI DRV8837/37C/38

Created by: florolf

• Provide a URL to a datasheet for the symbol(s) you are contributing
• http://www.ti.com/lit/ds/symlink/drv8837.pdf
• http://www.ti.com/lit/ds/symlink/drv8837c.pdf
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required