cnss: Turn on/off WLAN IO regulator and XTAL regulator properly

Currently 1.8V IO regulator and 1.8V XTAL regulator of WLAN are always on.
Turn on/off them when WLAN host driver is loading/unloading to avoid
current leakage.

Change-Id: I4730915c20d52b5009bcc16ad4496834824e792d
CRs-fixed: 759131
Signed-off-by: Yue Ma <yuem@codeaurora.org>