pcie: Remove redundant test in pcie_mmcfg_data_{read,write}()

pcie: Remove redundant test in pcie_mmcfg_data_{read,write}()

These functions have an explicit test for accesses above the device's
config size.  But pci_host_config_{read,write}_common() which they're
about to call already have checks against the config space limit and
do the right thing.  So, remove the redundant tests.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20190424041959.4087-2-david@gibson.dropbear.id.au>