EmbeddedPkg/AndroidFastboot: drop dependency on the LinuxLoader

EmbeddedPkg/AndroidFastboot: drop dependency on the LinuxLoader

When booting the kernel via Fastboot, invoke the kernel image directly
rather than passing it to the LinuxLoader app. This requires the kernel
image to be built with UEFI stub support.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Ryan Harkin <ryan.harkin@linaro.org>