common: fdt_support: Support special case of PCI address in fdt_read_prop()

common: fdt_support: Support special case of PCI address in fdt_read_prop()

At present fdt_read_prop() can only handle 1 or 2 cells. It is
called by fdt_read_range() which may be used to read PCI address
from <ranges> for a PCI bus node where the number of PCI address
cell is 3. The <ranges> property is an array of:

  { <child address> <parent address> <size in child address space> }

When trying to read <child address> from a PCI bus node using
fdt_read_prop(), as the codes below:

    /* Read <child address> */
    if (child_addr) {
        r = fdt_read_prop(ranges, ranges_len, cell, child_addr,
                          acells);
        if (r)
            return r;
    }

it will fail, because the PCI child address is made up of 3 cells
but fdt_read_prop() cannot handle it. We advance the cell offset
by 1 so that the <child address> can be correctly read.

This adds the special handling of such case.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>