libax25: add package
ax25-apps: add package
ax25-tools: add package
ax25-tools: add mkiss and ax25 kernel modules to RRCOMMENDS
recipes-kernel: add hamradio configurations

Currently, AX25 protocol and MKISS are enabled. I don't have BAYCOM
device to test, so it was disabled. It can be enabled later on
recipes-kernel: Add usb-serial.cfg, make ax25 built-in

Usb-serial.cfg adds configuration fragment for the most widely used
usb-serial converter FTDI.

Since this is a hamradio layer, add ax25 functionality in the kernel
built-in.
ax25-tools: add axports configuration template

kissattach and other programs require /etc/ax25/axports file to be
present. ax25-tools does not install the file by default. Add the file
with a decent documentation commented.
Merge pull request #2 from eren/master

Add libax25, ax25-{apps, tools} and kernel configurations for hamradio