hw: register: Run post_write hook on reset

hw: register: Run post_write hook on reset

Ensure that the post write hook is called during reset. This allows us
to rely on the post write functions instead of having to call them from
the reset() function.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: d131e24b911653a945e46ca2d8f90f572469e1dd.1517856214.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>