clk: sunxi: clk-mod0: Demote non-conformant kernel-doc header

Fixes the following W=1 kernel build warning(s):

 drivers/clk/sunxi/clk-mod0.c:24: warning: Function parameter or member 'req' not described in 'sun4i_a10_get_mod0_factors'

Cc: "Emilio López" <emilio@elopez.com.ar>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Cc: linux-clk@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210120093040.1719407-19-lee.jones@linaro.org