arm-toolchain: gcc-arm-none-eabi-native: Add recipe

Adds a recipe to pull down the prebuilt GCC for compiling on Cortex-R
and Cortex-M processors from ARM. This toolchain is required to build
Arm Trusted Firmware for the Rockchip rk3399 SoC, since it must compile
some firmware for the M0 coprocessor.

This was originally taken from meta-rockchip, but has been modified from
mailing list feedback.

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Denys Dmytriyenko <denys@ti.com>
Reviewed-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>