video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host

Beginning from Windows 10 RS5+, VM screen resolution is obtained from host.
The "video=hyperv_fb" boot time option is not needed, but still can be
used to overwrite what the host specifies. The VM resolution on the host
could be set by executing the powershell "set-vmvideo" command.

Signed-off-by: Iouri Tarassov <iourit@microsoft.com>
Signed-off-by: Wei Hu <weh@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>