drm/hyperv: Fix double mouse pointers

drm/hyperv: Fix double mouse pointers

Hyper-V supports a hardware cursor feature. It is not used by Linux VM,
but the Hyper-V host still draws a point as an extra mouse pointer,
which is unwanted, especially when Xorg is running.

The hyperv_fb driver uses synthvid_send_ptr() to hide the unwanted pointer.
When the hyperv_drm driver was developed, the function synthvid_send_ptr()
was not copied from the hyperv_fb driver. Fix the issue by adding the
function into hyperv_drm.

Fixes: aebd89482ab4 ("drm/hyperv: Add DRM driver for hyperv synthetic video device")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Deepak Rawat <drawat.floss@gmail.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210916193644.45650-1-decui@microsoft.com
Signed-off-by: Dave Airlie <airlied@redhat.com>