qcacmn: Cleanup CE poll implementation

Change CE poll timer to wake up CPU so that timer kicks in even though
CPU is in idle state. This is needed so that poll happens in regular
10ms intervals. Also made ce_inited false during wifi down path to
prevent polling during wifi down.

Also made some cleanup in polling implementation to remove global scn
flag to enable polled mode and use attr flag to enable per CE polling.

Change-Id: I1d894c99193cc9902fcf4d6cbfd179c557ec6219
CRs-fixed: 2269599
6 files changed