The CPU variable in the boards Makefile.include file already contains the target
CPU, so there is no reason to provide it in each board again as avrdude flag.
This commit automatically sets the avrdude target from the CPU variable and
removes the unneeded flags.
Leverages common flasher (avrdude) and removes unnecessary exports.
Moreover, a reuse of serial.inc.mk is perfomed from the same
atmega_common/Makefile.include
The file always exist so no need to do '-include'.
Replaced using:
sed -i 's|-\(include $(RIOTCPU)/.*/Makefile.features\)|\1|' \
$(git grep -l '$(RIOTCPU)/.*/Makefile.features' boards)
Uno and Duemilanove(atmega328p version) are nearly the same boards.
The only difference is that the Duemilanove use an FTDI usb chip,
while the Uno use an Atmel which acts as USB/Serial converter.
All of the code needed to support these boards is in arduino-common.
