ext: Import Atmel SAM E70 header files from ASF library

Atmel Software Framework (ASF) provides a set of low-level
header files that give access to different hardware
peripherals of Atmel's ICs.

Origin: Atmel SAME70 Series Device Support (2.0.78)
URL: http://packs.download.atmel.com/Atmel.SAME70_DFP.2.0.78.atpack


License: Apache-2.0
Maintained-by: External

Jira: ZEP-976
Change-Id: I81c2cff3c4a05502c712d71c883650a16c9bb228
Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>