efi: Move common EFI stub code from x86 arch code to common location

efi: Move common EFI stub code from x86 arch code to common location

No code changes made, just moving functions and #define from x86 arch
directory to common location.  Code is shared using #include, similar
to how decompression code is shared among architectures.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Mark Salter <msalter@redhat.com>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
(cherry picked from commit 7721da4c1ebf96ff815987011c1a0edef596b50a)
Signed-off-by: Mark Brown <broonie@linaro.org>
Conflicts:
	arch/x86/boot/compressed/eboot.c
	arch/x86/boot/compressed/eboot.h