clk: renesas: div6: Document fields used for parent selection

Add the missing documentation for the fields in struct div6_clock
related to parent selection for DIV6 clocks with selectable parents, as
found in R/SH-Mobile SoCs.

Fixes: c6d67fb0 ("clk: shmobile: div6: support selectable-input clocks")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

drivers/clk/renesas/clk-div6.c

@@ -29,6 +29,9 @@
  * @hw: handle between common and hardware-specific interfaces
  * @reg: IO-remapped register
  * @div: divisor value (1-64)
+ * @src_shift: Shift to access the register bits to select the parent clock
+ * @src_width: Number of register bits to select the parent clock (may be 0)
+ * @parents: Array to map from valid parent clocks indices to hardware indices
  */
 struct div6_clock {
 	struct clk_hw hw;