The DWC core driver already parses and stores the 'num-viewport' DT
property, so there is no need for the Keystone driver to store it.

Link: https://lore.kernel.org/r/20200821035420.380495-21-robh@kernel.orgSigned-off-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>