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

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

[ Upstream commit d1403f4b6d62ea4ea03d96d99bccf2245463523c ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>