clk: Prepare to remove asm-generic/clkdev.h

Now that all the users of asm/clkdev.h have been replaced with
the generic file we can get rid of the asm-generic file as well
and implement that code directly where it's used.

We only have one caller of __clkdev_alloc(), in clkdev.c so we
can easily remove that and drop the include of asm/clkdev.h in
linux/clkdev.h by putting the __clk_get/__clk_put inlines in
their respective location.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>