asoc: fsa8500: Improve slow insertion detection

If 3-pole headset is inserted slowly it may be detected by FSA8500 as
a 4-pole hs and a key long press will be reported right away.
To fix this problem reset detection state if a key event came less then
2 sec after a headset is plugged in.

Change-Id: I08c25ed3f195d273cb2a711ec09b83ed8ae8637a
Signed-off-by: Vladimir Karpovich <vkarpovich@motorola.com>