UPSTREAM: lib/vdso: Let do_coarse() return 0 to simplify the callsite

do_coarse() is similar to do_hres() except that it never fails.

Change its type to int instead of void and let it always return success (0)
to simplify the call site.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/21e8afa38c02ca8672c2690307383507fe63b454.1577111367.git.christophe.leroy@c-s.fr


(cherry picked from commit 8463cf80529d0fd80b84cd5ab8b9b952b01c7eb9)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: Ia57b47a7ed90e102fa3323311d998b2f77989bda