[PATCH] drm/hyperv: Don't overwrite dirt_needed value set by host

[Dexuan Cui]

> From: Saurabh Sengar <ssengar at linux.microsoft.com>
> Sent: Monday, September 12, 2022 8:33 AM
>  ...
> Existing code is causing a race condition where dirt_needed value is
> already set by the host and gets overwritten with default value. Remove
> this default setting of dirt_needed, to avoid overwriting the value
> received in the channel callback set by vmbus_open. Removing this
> setting also means the default value for dirt_needed is changed to false
> as it's allocated by kzalloc which is similar to legacy hyperv_fb driver.
> 
> Signed-off-by: Saurabh Sengar <ssengar at linux.microsoft.com>

Reviewed-by: Dexuan Cui <decui at microsoft.com>