TLC5957 & TLC5951

Created by: s-light

adding

• TLC5951 (24-Channel, 12-Bit PWM LED Driver)
• TLC5957 (48-Channel, 16-Bit ES-PWM LED Driver)

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Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the symbol(s) you are contributing
  • TLC5951
  • TLC5957
• 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
  • HTSSOP-38-1EP* https://github.com/KiCad/kicad-footprints/pull/1029
  • QFP40 → blocked by https://github.com/KiCad/kicad-footprints/issues/606#issuecomment-431347500
  • QFN*56 EP5.6 → https://github.com/KiCad/kicad-footprints/pull/1031
• Check the output of the Travis automated check scripts - fix any errors as required