clk: Add missing documentation of devm_clk_bulk_get_optional() argument

Fix an incomplete devm_clk_bulk_get_optional() function documentation
by adding description of the num_clks argument as in other *clk_bulk*
functions.

Fixes: 9bd5ef0b ("clk: Add devm_clk_bulk_get_optional() function")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

include/linux/clk.h

@@ -359,6 +359,7 @@ int __must_check devm_clk_bulk_get(struct device *dev, int num_clks,
 /**
  * devm_clk_bulk_get_optional - managed get multiple optional consumer clocks
  * @dev: device for clock "consumer"
+ * @num_clks: the number of clk_bulk_data
  * @clks: pointer to the clk_bulk_data table of consumer
  *
  * Behaves the same as devm_clk_bulk_get() except where there is no clock