dp8393x: Use long-word-aligned RRA pointers in 32-bit mode

dp8393x: Use long-word-aligned RRA pointers in 32-bit mode

Section 3.4.1 of the datasheet says,

    The alignment of the RRA is confined to either word or long word
    boundaries, depending upon the data width mode. In 16-bit mode,
    the RRA must be aligned to a word boundary (A0 is always zero)
    and in 32-bit mode, the RRA is aligned to a long word boundary
    (A0 and A1 are always zero).

This constraint has been implemented for 16-bit mode; implement it
for 32-bit mode too.

Signed-off-by: Finn Thain <[email protected]>
Tested-by: Laurent Vivier <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Jason Wang <[email protected]>