ARM: mach-shmobile: clock-sh7372: remove bogus pllc2 clock toggling.

The PLLC2 clock was utilizing the same sort of enable/disable without
regard to usecount approach that the FSIDIV clock was when being used as
a PLL pass-through. This forces the enable/disable through the clock
framework, which now prevents the clock from being ripped out or modified
underneath users that have an existing handle on it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>