atheros: fix too short msleep

Use msleep(20) instead of msleep(10) to make code closer to reality
since msleep can sleep for up to 20ms even we request shorter delay.
All updated calls are located in PCI initialization routine which is
called only once upon device boot. So there should be no performance
issues caused by more longer delay.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>

SVN-Revision: 41096