sh: Use generic clkdev.h header

The generic header file is almost equivalent to the SH one. The
only difference is that the SH one supports allocating clkdev
lookups early using bootmem allocators instead of the slabs. From
what I can tell using visual inspection, the slab is initialized
before any clkdev allocation is made under arch/sh. So let's
remove the arch specific clkdev.h header and use the generic one
instead.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rich Felker <dalias@libc.org>