clk: renesas: rcar-gen3: Remove unused variable

This variable is no longer used and the compiler rightly complains that
it should be removed. Drop it to silence the following:

drivers/clk/renesas/rcar-gen3-cpg.c: In function 'cpg_sd_clk_register':
drivers/clk/renesas/rcar-gen3-cpg.c:386:15: warning: unused variable 'i' [-Wunused-variable]
  unsigned int i;

Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: b953eaae ("clk: renesas: rcar-gen3: Fix cpg_sd_clock_round_rate() return value")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>