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 <[e-mail]>
Cc: Jiri Slaby <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Peter Waskiewicz <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/pch_uart.c

···
 #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;
···
 	if (cmp && (strstr(cmp, "COMe-mTT") ||
 		    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;
 }