PCI: mobiveil: Clear the control fields before updating it

While programming the inbound and outbound windows in

program_{ib/ob}_windows()

we shoud clear the control fields in the registers before programming
it with a new value to prevent stale bits from older configuration.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Reviewed-by: Subrahmanya Lingappa <l.subrahmanya@mobiveil.co.in>