perf: Export perf_event_update_userpage

perf: Export perf_event_update_userpage

BugLink: https://launchpad.net/bugs/1811200
Export perf_event_update_userpage() so that PMU driver using them,
can be built as modules.

Acked-by: Peter Zilstra <peterz@infradead.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 82975c46da8275a2a212cd94049bbef9bb961da2)
Signed-off-by: Ike Panhc <ike.pan@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>