video: sh_mobile_lcdcfb: depends on HAVE_CLK.

This deifdefs the driver and adds an explicit HAVE_CLK dependency. Given
that all SH platforms provide it, there is no reason to keep this as an
ifdef. Other architectures that implement support for this driver will
already have to provide clock framework support for timers and so on
already, so adding this as an additional dependency is not terribly
probematic.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>