bus: mvebu-mbus: provide api for obtaining IO and DRAM window information

This commit enables finding appropriate mbus window and obtaining its
target id and attribute for given physical address in two separate
routines, both for IO and DRAM windows. This functionality
is needed for Armada XP/38x Network Controller's Buffer Manager and
PnC configuration.

[gregory.clement@free-electrons.com: Fix size test for
mvebu_mbus_get_dram_win_info]

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
[DRAM window information reference in LKv3.10]
Signed-off-by: Evan Wang <xswang@marvell.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>