UPSTREAM: arm64: vdso32: Include common headers in the vdso library

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.

Refactor the vdso32 implementation to include common headers.

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/20200320145351.32292-22-vincenzo.frascino@arm.com


(cherry picked from commit 5340e873576ee04186eca3c70844c576d714cc6a)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: I7ab0a1b114185a609e522cfe77efd19599f117a5