Now that hrtimers are always running in hard irq context we can't
unconditionally enable interrupts at the end of the timer function.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Kwangwoo Lee <kwangwoo.lee@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>