clk: Drop !clk checks in debugfs dumping

These recursive functions have checks for !clk being passed in, but the
callers are always looping through lists and therefore the pointers
can't be NULL. Drop the checks to simplify the code.

Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20190826234729.145593-1-sboyd@kernel.org