clk: rockchip: fix error for unknown clocks

There is a clk == NULL check after the switch to check for
unsupported clk types. Since clk is re-assigned in a loop,
this check is useless right now for anything but the first
round. Let's fix this up by assigning clk = NULL in the
loop before the switch statement.

Fixes: a245fecb ("clk: rockchip: add basic infrastructure for clock branches")
Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
[added fixes + stable-cc]
Link: https://lore.kernel.org/r/20240325193609.237182-6-sebastian.reichel@collabora.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>