of: base: Document prefix argument for of_get_next_child_with_prefix()

of: base: Document prefix argument for of_get_next_child_with_prefix()

When of_get_next_child_with_prefix() was added, the prefix argument was
left undocumented. This caused a new warning to be generated during the
kerneldoc build process:

 drivers/of/base.c:661: warning: Function parameter or struct member 'prefix'
 	not described in 'of_get_next_child_with_prefix'

Properly document the argument to fix this.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202411280010.KGSDBOUE-lkp@intel.com/
Fixes: 1fcc67e3a354 ("of: base: Add for_each_child_of_node_with_prefix()")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>