clk: __clk_core_init() never takes NULL

The only caller of __clk_core_init() allocates the pointer and checks
the allocation for NULL so this check is impossible. Remove it.

Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20211208041534.3928718-2-sboyd@kernel.org