The driver currently checks the clk pointer for an error condition, as
returned by clk_get, before every invocation of the clk consumer API.
This is redundant if the goal is simply to ignore the errors, thereby
making the clk optional. The clk consumer API already checks if the
pointer is NULL or not.

Simplify the code a bit by assigning NULL to the clk pointer if the
error condition is one we want to ignore, which is every error except
deferred probing.
Tested-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>