linksys-jamaica: add mainline support

device/testing/device-linksys-jamaica/APKBUILD

device/testing/device-linksys-jamaica/boot-image.its

device/testing/device-linksys-jamaica/deviceinfo

device/testing/device-linksys-jamaica/initfs-hook.sh

device/testing/linux-linksys-jamaica/001-fix-build.patch

.../testing/linux-linksys-jamaica/412_ipq5018-pwm-leds.patch

...etfilter-br_netfilter-Don-t-invoke-iptables-by-defa.patch

device/testing/linux-linksys-jamaica/APKBUILD

...g/linux-linksys-jamaica/add-linksys-jamaica-support.patch

device/testing/linux-linksys-jamaica/armv7.patch

...esting/linux-linksys-jamaica/config-linksys-jamaica.armv7

device/testing/linux-linksys-jamaica/jamaica.patch

...RM-8933-1-replace-Sun-Solaris-style-flag-on-section.patch