serial: sh-sci: Depend on HAVE_CLK unconditionally.

The sh-sci code conditionalized the clock framework support in order to
give the other platforms a chance to catch up. sh64 supported this some
time ago and the forthcoming ARM changes handle this as well, this leaves
h8300 as the odd one out. H8300 has had since 2.5 to merge it's sh-sci
support upstream, and has yet to do so. At this point I will no longer be
holding back the driver to support an unreponsive architecture, 7 years
is quite enough of a grace period. Support is easily implemented on the
architecture if and when it ever decides to merge its changes upstream.

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