UPSTREAM: arm64: Introduce asm/vdso/processor.h

The vDSO library should only include the necessary headers required for
a userspace library (UAPI and a minimal set of kernel headers). To make
this possible it is necessary to isolate from the kernel headers the
common parts that are strictly necessary to build the library.

Introduce asm/vdso/processor.h to contain all the arm64 specific
functions that are suitable for vDSO inclusion.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200320145351.32292-20-vincenzo.frascino@arm.com


(cherry picked from commit f511e079177a9b97175a9a3b0ee2374d55682403)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: I9a291dc86b9c7c910331811c2f3c93db7406e956