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

 drivers/clk/imx/clk-imx31.c:54:28: warning: ‘uart_clks’ defined but not used [-Wunused-const-variable=]

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Arnd Bergmann <arnd@arndb.de>
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: Shawn Guo <shawnguo@kernel.org>