clk: sunxi: a20-gmac: fix kernel-doc warnings

clk: sunxi: a20-gmac: fix kernel-doc warnings

Move the function kernel-doc comment to be immediately before the
function implementation, then add a function parameter description
to prevent kernel-doc warnings:

clk-a20-gmac.c:43: warning: expecting prototype for sun7i_a20_gmac_clk_setup(). Prototype was for SUN7I_A20_GMAC_GPIT() instead
clk-a20-gmac.c:53: warning: Function parameter or struct member 'node' not described in 'sun7i_a20_gmac_clk_setup'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Emilio López <emilio@elopez.com.ar>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc:  <linux-clk@vger.kernel.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Samuel Holland <samuel@sholland.org>
Cc:  <linux-arm-kernel@lists.infradead.org>
Cc:  <linux-sunxi@lists.linux.dev>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20240121051837.17564-1-rdunlap@infradead.org
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>