lpac: make APDU backends configurable

lpac: make APDU backends configurable

Currently, lpac will be built with the PCSC and AT APDU backends by default
and its not configurable in OpenWrt.

Since smart card reads are not really common on OpenWrt devices lets
disable PCSC backend by default so we dont have to include PCSC lib and
daemon by default.

AT backend is left enabled by default since it has no external dependecies
and all modems have it.

QMI over QRTR backend is not selectable even though it is part of the 2.0.2
relase since it requires unstable libqmi 1.35.4 or newer and we are still
using 1.34 stable branch.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>