Replace the custom minimal clock implementation for Toshiba TXx9 by a
basic implementation using the Common Clock Framework.

The only clocks that are provided are those needed by TXx9-specific
drivers ("imbus" and "spi" (TX4938 only)), and their common parent
clock "gbus". Other clocks can be added when needed.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Guenter Roeck <linux@roeck-us.net>
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/14239/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>