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>

include/clk.h

@@ -21,7 +21,7 @@
  *
  * A driver that implements UCLASS_CLOCK is a clock provider. A provider will
  * often implement multiple separate clocks, since the hardware it manages
- * often has this capability. clock_uclass.h describes the interface which
+ * often has this capability. clk-uclass.h describes the interface which
  * clock providers must implement.
  *
  * Clock consumers/clients are the HW modules driven by the clock signals. This