package/c-periphery: bump version to 2.1.0

Since commit "gpio: add cdev implementation"
(https://github.com/vsergeev/c-periphery/commit/d0a973cca2eca8c3b84013ade210849ce4e2a2af

),
c-periphery needs linux headers >= 4.8.

The hash of the license file is updated due to an update in the
copyright year:

  - Copyright (c) 2014-2016 vsergeev / Ivan (Vanya) A. Sergeev
  + Copyright (c) 2014-2019 vsergeev / Ivan (Vanya) A. Sergeev

Signed-off-by: Joris Offouga <offougajoris@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>