Revert "DXVA: also reset the hwaccel hooks when resetting the hardware"

This reverts commit 2f7984da53e09cba3fd1106b144bc8300f11da9b.
Revert "Close the DXVA2 decoder before opening again"

This reverts commit 315032321ab805d3692fff04811077c49271f382.
Alternate DXVA fix

If the context already has a DXVA decoder use it rather than making a
new instance.