Fix live timer calculation error

There is an calculation error for live timer. Variable
switch_timer_interval is based on microsecond, and it is not
right to assign switch_timer_interval mod 1000000 to var tv_nsec
which is based on nanosecond.

Signed-off-by: Mikael Beckius <mikael.beckius@windriver.com>
Signed-off-by: Jianchuan Wang <jianchuan.wang@windriver.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>