drm/hyperv: Handle feature change message from device

Virtual device inform if screen update is needed or not with
SYNTHVID_FEATURE_CHANGE message. Handle this message to set dirt_needed
flag.

Suggested-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Deepak Rawat <drawat.floss@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210527112230.1274-2-drawat.floss@gmail.com