iio: frequency: adf4377: Fully initialize clk_init_data and clk_parent_data

In the Linux kernel, the following vulnerability has been resolved: iio: frequency: adf4377: Fully initialize clk_init_data and clk_parent_data The clk_init_data structure contains several mutually-exclusive members for different methods to specify the possible parents of a clock, prompting drivers to initialize only the members they need. However, not initializing all members may cause subtle issues, which are only exposed when CONFIG_INIT_STACK_ALL_PATTERN or CONFIG_INIT_STACK_NONE is enabled. adf4377_clk_register() fills in init.parent_data, and assumes that init.parent_names is NULL. However, the latter is uninitialized, and thus may cause a crash. Similarly, adf4377_clk_register() fills in only parent_data.fw_name, leaving other members of the clk_parent_data structure uninitialized. Make sure all members are fully initialized, to fix such bugs, and to avoid future breakage when converting drivers to a different method for specifying the parents.