WATCHDOG: txx9wdt: Add missing clock (un)prepare calls for CCF

While the custom minimal TXx9 clock implementation doesn't need or use
clock (un)prepare calls (they are dummies if !CONFIG_HAVE_CLK_PREPARE),
they are mandatory when using the Common Clock Framework.

Hence add them, to prepare for the advent of CCF.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-clk@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-watchdog@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14238/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>