tty: ar933x_uart: use the clk API to get the uart clock

The AR933x UARTs are only used on the Atheros AR933x
SoCs. The base clock frequency of the UART is passed
to the driver via platform data. The SoC support code
implements the generic clock API, and the clock rate
can be retrieved via that.

Update the code to get the clock rate via the generic
clock API instead of using the platform data.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index f136248..3c598e3 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1402,7 +1402,7 @@
 
 config SERIAL_AR933X
 	bool "AR933X serial port support"
-	depends on SOC_AR933X
+	depends on HAVE_CLK && SOC_AR933X
 	select SERIAL_CORE
 	help
 	  If you have an Atheros AR933X SOC based board and want to use the