clk: zynqmp: fix kerneldoc of __zynqmp_clock_get_parents

The kerneldoc refers to __zynqmp_clock_get_topology(), but actually
documents __zynqmp_clock_get_parents(). Refer to the correct function
name in the kerneldoc.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>