pch_uart: Add uart_clk selection for the MinnowBoard

Use DMI_BOARD_NAME to determine if we are running on a MinnowBoard and
set the uart clock to 50MHz if so. This removes the need to pass the
user_uartclk to the kernel at boot time.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Waskiewicz <peter.p.waskiewicz.jr@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pch_uart.c

@@ -217,6 +217,7 @@ enum {
 #define FRI2_64_UARTCLK  64000000 /*  64.0000 MHz */
 #define FRI2_48_UARTCLK  48000000 /*  48.0000 MHz */
 #define NTC1_UARTCLK     64000000 /*  64.0000 MHz */
+#define MINNOW_UARTCLK   50000000 /*  50.0000 MHz */
 
 struct pch_uart_buffer {
 	unsigned char *buf;
@@ -398,6 +399,10 @@ static int pch_uart_get_uartclk(void)
 		    strstr(cmp, "nanoETXexpress-TT")))
 		return NTC1_UARTCLK;
 
+	cmp = dmi_get_system_info(DMI_BOARD_NAME);
+	if (cmp && strstr(cmp, "MinnowBoard"))
+		return MINNOW_UARTCLK;
+
 	return DEFAULT_UARTCLK;
 }