hw/char: Convert the Ibex UART to use the qdev Clock model

Conver the Ibex UART to use the recently added qdev-clock functions.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: b0136fad870a29049959ec161c1217b967d7e19d.1594332223.git.alistair.francis@wdc.com
Message-Id: <b0136fad870a29049959ec161c1217b967d7e19d.1594332223.git.alistair.francis@wdc.com>