BACKPORT: efi/libstub/arm64: Force 'hidden' visibility for section markers

To prevent the compiler from emitting absolute references to the section
markers when running in PIC mode, override the visibility to 'hidden' for
all contents of asm/sections.h

Tested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170818194947.19347-4-ard.biesheuvel@linaro.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 0426a4e68f18d75515414361de9e3e1445d2644e)
Signed-off-by: Greg Hackmann <ghackmann@google.com>

Change-Id: Ia438c3f0aa6abdbd9057dfe1db732a25aa98ef40