PCI: designware: Fix configuration base address when using 'reg'

The code has calculated cfg0_base and cfg1_base when parsing 'reg' or
'ranges' property of PCI DTS node, so remove duplicate calculation.  When
using 'reg', resource cfg is not used, so this code computed an incorrect
configuration base.

Signed-off-by: Minghuan Lian <Minghuan.Lian@freescale.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Mohit KUMAR <mohit.kumar@st.com>