ArmPkg: remove the LinuxLoader application

ArmPkg: remove the LinuxLoader application

The LinuxLoader application boots Linux in a way that prevents the OS
from accessing UEFI runtime services. Since we have better ways now
of invoking the kernel (via GRUB, or directly via the kernel's UEFI
stub), remove the obsolete LinuxLoader so that people will no longer
mistake it for a suitable reference of how to invoke the OS from UEFI.

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>