efi/x86: Move the EFI BGRT init code to early init code

Before invoking the arch specific handler, efi_mem_reserve() reserves
the given memory region through memblock.

efi_bgrt_init() will call efi_mem_reserve() after mm_init(), at which
time memblock is dead and should not be used anymore.

The EFI BGRT code depends on ACPI initialization to get the BGRT ACPI
table, so move parsing of the BGRT table to ACPI early boot code to
ensure that efi_mem_reserve() in EFI BGRT code still use memblock safely.

Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-acpi@vger.kernel.org
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1485868902-20401-9-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>