arm64: efi: add EFI stub

arm64: efi: add EFI stub

This patch adds PE/COFF header fields to the start of the kernel
Image so that it appears as an EFI application to UEFI firmware.
An EFI stub is included to allow direct booting of the kernel
Image.

Signed-off-by: Mark Salter <msalter@redhat.com>
[Add support in PE/COFF header for signed images]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
(cherry picked from commit 3c7f255039a2ad6ee1e3890505caf0d029b22e29)
Signed-off-by: Mark Brown <broonie@linaro.org>
Conflicts:
	arch/arm64/Kconfig
	arch/arm64/kernel/Makefile