wil6210: disallow changing power save profile while in VR mode

When in VR mode, driver disables FW power management. When interface
is up OS may try to enable power management again.
Disallow changing power save profile while in VR mode.

Change-Id: I5ef791463e7488ba5e22ac5702f487eb462bca7d
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>
Signed-off-by: Ahmad Masri <amasri@codeaurora.org>