clkdev: remove unused clkdev_alloc() interfaces

The last user of clkdev_alloc() and clkdev_hw_alloc() was
removed last year, so everything now calls clkdev_create()
and clkdev_hw_create() instead.

Removing the unused functions lets the compiler optimize
the remaining ones slightly better.

Fixes: e5006671 ("clk: versatile: Drop the legacy IM-PD1 clock code")
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>