UPSTREAM: lib/vdso: Avoid duplication in __cvdso_clock_getres()

VDSO_HRES and VDSO_RAW clocks are handled the same way.

Avoid the code duplication.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/fdf1a968a8f7edd61456f1689ac44082ebb19c15.1577111367.git.christophe.leroy@c-s.fr


(cherry picked from commit cdb7c5a9c897ab2e5c56df647dd84c84e150e925)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: I765c9ddf53427d970e8b186cf4d37623c9218f25