Current there is no way to split code between ATmega and ATxmega in
drivers. This differentiate AVR8 cores into MEGAs and XMEGAs.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
Split atmega_common code into avr8_common folder. This moves common
avr8 code to be used for all avr8 variants: tiny, mega and xmega.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>