sh: Derive calibrate_delay lpj from clk fwk.

All CPUs must have a sensible cpu_clk definition these days, which we can
safely use for deriving the preset loops_per_jiffy. The only odd one out
is SH-5, which hasn't been hammered in to the framework yet.

Based on the ST patch.

Signed-off-by: Francesco Virlinzi <francesco.virlinzi@st.com>
Signed-off-by: Carl Shaw <carl.shaw@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>