clk: zynq: clkc: Remove various instances of an unused variable 'clk'

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

 drivers/clk/zynq/clkc.c: In function ‘zynq_clk_register_fclk’:
 drivers/clk/zynq/clkc.c:106:14: warning: variable ‘clk’ set but not used [-Wunused-but-set-variable]
 drivers/clk/zynq/clkc.c: In function ‘zynq_clk_register_periph_clk’:
 drivers/clk/zynq/clkc.c:179:14: warning: variable ‘clk’ set but not used [-Wunused-but-set-variable]
 drivers/clk/zynq/clkc.c: In function ‘zynq_clk_setup’:
 drivers/clk/zynq/clkc.c:220:14: warning: variable ‘clk’ set but not used [-Wunused-but-set-variable]

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "Sören Brinkmann" <soren.brinkmann@xilinx.com>
Cc: linux-clk@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210120093040.1719407-21-lee.jones@linaro.orgSigned-off-by: Stephen Boyd <sboyd@kernel.org>