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>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 82e21de..6c71f12 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -290,8 +290,9 @@
 	help
 	  This option provides support for runtime services provided
 	  by UEFI firmware (such as non-volatile variables, realtime
-          clock, and platform reset). This is only useful on systems
-	  that have UEFI firmware.
+          clock, and platform reset). A UEFI stub is also provided to
+	  allow the kernel to be booted as an EFI application. This
+	  is only useful on systems that have UEFI firmware.
 
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