clk: socfpga: clk-pll-a10: Remove set but unused variable 'rc'

clk: socfpga: clk-pll-a10: Remove set but unused variable 'rc'

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

 drivers/clk/socfpga/clk-pll-a10.c: In function ‘__socfpga_pll_init’:
 drivers/clk/socfpga/clk-pll-a10.c:76:6: warning: variable ‘rc’ set but not used [-Wunused-but-set-variable]

Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: linux-clk@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210120093040.1719407-9-lee.jones@linaro.org
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>