soc/intel/fsp_broadwell_de/uart: Drop it

A copy of our uart8250io driver sneaked in with Broadwell-DE support.
The only difference is the lack of initialization (due to FSP handling
that).

TEST=manually compared resulting object files

Change-Id: I09be10b76c76c1306ad2c8db8fb07794dde1b0f2
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/16786
Tested-by: build bot (Jenkins)
Reviewed-by: York Yang <york.yang@intel.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/drivers/uart/Kconfig

@@ -9,6 +9,10 @@ config DRIVERS_UART_8250IO
 	default n if NO_UART_ON_SUPERIO
 	default y if ARCH_X86
 
+config DRIVERS_UART_8250IO_SKIP_INIT
+	def_bool n
+	depends on DRIVERS_UART_8250IO
+
 # Select this for mainboard without SuperIO serial port.
 config NO_UART_ON_SUPERIO
 	def_bool n

src/drivers/uart/uart8250io.c

@@ -104,10 +104,12 @@ uintptr_t uart_platform_base(int idx)
 
 void uart_init(int idx)
 {
-	unsigned int div;
-	div = uart_baudrate_divisor(default_baudrate(), uart_platform_refclk(),
-		uart_input_clock_divider());
-	uart8250_init(uart_platform_base(idx), div);
+	if (!IS_ENABLED(CONFIG_DRIVERS_UART_8250IO_SKIP_INIT)) {
+		unsigned int div;
+		div = uart_baudrate_divisor(default_baudrate(),
+			uart_platform_refclk(), uart_input_clock_divider());
+		uart8250_init(uart_platform_base(idx), div);
+	}
 }
 
 void uart_tx_byte(int idx, unsigned char data)