[bug #49972] avr/wdt: Fix support for atxmega devices

[avrs-admin]

Mon 02 Jan 2017 05:38:59 PM CET

On Xmega PER is located at bit 2, not at bit 0. Also the first timeout
is 8ms not 16, which means that me must add one to original PER value.

Checkout
page122
http://www.atmel.com/Images/doc8077.pdf
page 129
http://www.atmel.com/images/Atmel-42005-8-and-16-bit-AVR-Microcontrollers-XMEGA-E_Manual.pdf
page 127
http://www.atmel.com/Images/Atmel-8331-8-and-16-bit-AVR-Microcontroller-XMEGA-AU_Manual.pdf

file #39342: 0001-avr-wdt-Fix-support-for-atxmega-devices.patch

This issue was migrated from https://savannah.nongnu.org/bugs/?49972