mailbox: imx: add support for imx v1 mu

There is a version 1.0 MU on i.MX7ULP platform.
One new version ID register is added, and it's offset is 0.
TRn registers are defined at the offset 0x20 ~ 0x2C.
RRn registers are defined at the offset 0x40 ~ 0x4C.
SR/CR registers are defined at 0x60/0x64.
Extend this driver to support it.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Suggested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>