FROMLIST: BACKPORT: [PATCH 3/6] arm64: Refactor vDSO init/setup

FROMLIST: BACKPORT: [PATCH 3/6] arm64: Refactor vDSO init/setup

(cherry pick from url https://patchwork.kernel.org/patch/10060439/)

Move the logic for setting up mappings and pages for the vDSO into
static functions. This makes the vDSO setup code more consistent with
the compat side and will allow to reuse it for the future compat vDSO.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Bug: 63737556
Bug: 20045882
Change-Id: I13e84479591091669190360f2a7f4d04462e6344