clk: imx: remove clk_count of imx_register_uart_clocks

The clk count has been get with of_clk_get_parent_count, there is
no need to pass clk_count from users.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230104110032.1220721-4-peng.fan@oss.nxp.com