wil6210: support VR profiles

Allow wil6210 to configure the system in Virtual Reality (VR) mode.
When system is in VR mode it should have a low latency, and a high
responsive to events in the system. Wil6210 will set the rx interrupt
moderation to lower threshold and will drop packets when the transmit
queue is full.

Disallow changing power save profile while in VR mode.

New sysfs "vr_profile" can be used by userspace to enable and set
VR profile.

WMI_SET_VR_PROFILE_CMDID is used to configure the FW into different
VR profile configurations.

Change-Id: If9e0a5eb3323f1479d76b259c848310508e7009c
Signed-off-by: Ahmad Masri <amasri@codeaurora.org>
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>