PCI: dwc: Remove read_dbi2 code

PCI: dwc: Remove read_dbi2 code

The DBI2 appears to be write-only and there's no read accesses in the code
anyways, so let's remove all the read_dbi2 related code.

Link: https://lore.kernel.org/r/20200821035420.380495-33-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo 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>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>