At present the PCI BDF (bus/device/function) is needed to access the SPI
mapping, since the registers are at BAR0. This doesn't work when PCI
auto-config has not been done yet, since BARs are unassigned.
Add another way to find the mapping, using the MMIO base, if the caller
knows this.
Also add a missing function comment.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
8e2922e357