boards: intel_adsp_ace20_lnl: build with Zephyr SDK

intel_adsp_ace20_lnl can also build with intel_adsp_ace15_mtpm
toolchain in Zephyr SDK as the SoC is quite similar. This allows
twister to build in CI to avoid any breakage.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>