cmd: pci: add option to parse and display BAR information

Currently the PCI command only allows to see the BAR register
values but not the size and actual base address.
This little extension parses the BAR registers and displays
the base, size and type of each BAR.

Signed-off-by: Yehuda Yitschak <yehuday@marvell.com>
Reviewed-by: Simon Glass <sjg@chromium.org>