sh: fix a kfree address in clkdev code

kfree() in clkdev_drop() function should actually be called with an address of
a struct clk_lookup_alloc object, and not struct clk_lookup, as presently done.
This just happens to work, because "struct clk_lookup cl" is the first
member in struct clk_lookup_alloc.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>