include/clk.h: Fix the name of the clock uclass in comment

The comment references a structure name that doesn't exist. Use
the name of the actual uclass.

Signed-off-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
Drop period at end of commit subject:
Signed-off-by: Simon Glass <sjg@chromium.org>
1 file changed