virtio-gpu: Make non-gl display updates work again when blob=true

virtio-gpu: Make non-gl display updates work again when blob=true

In the case where the console does not have gl capability, and
if blob is set to true, make sure that the display updates still
work. Commit e86a93f55463 accidentally broke this by misplacing
the return statement (in resource_flush) causing the updates to
be silently ignored.

Fixes: e86a93f55463 ("virtio-gpu: splitting one extended mode guest fb into n-scanouts")
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20230623060454.3749910-1-vivek.kasireddy@intel.com>
(cherry picked from commit 34e29d85a7734802317c4cac9ad52b10d461c1dc)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>