Since the ATF project, we usually use the mmio_read_32 and
mmio_write_32. And the mmio_write_32, the firse parameter
is ADDR, the second is VALUE. In order to style consistency:

1/ rename readl/writel to mmio_read_32/mmio_write_32
2/ for keeping the same with mmio_write_32 in the ATF project,
   swap the order of the parameters for M0 mmio_write_32

Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Lin Huang <hl@rock-chips.com>