package/avrdude: optionally depends on libftdi or libftdi1

Avrdude supports both libftdi and libftdi1.

Because libftdi is already an optional dependency, this patch adds
libftdi1 as optional dependency as well, but privileges libftdi1 over
libftdi (accdording to what is done in  avrdude's configure script).

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>