superio/nsc/pc97317: Use link-time symbols over .c inclusion

Change-Id: Ia45bc7a880d0dab57c56a0452858cd26626f09df
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/8076
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/mainboard/compaq/deskpro_en_sff_p600/romstage.c

@@ -30,7 +30,7 @@
 #include "lib/delay.c"
 #include "cpu/x86/bist.h"
 /* FIXME: This should be PC97307 (but it's buggy at the moment)! */
-#include "superio/nsc/pc97317/early_serial.c"
+#include <superio/nsc/pc97317/pc97317.h>
 #include <lib.h>
 
 /* FIXME: This should be PC97307 (but it's buggy at the moment)! */

src/superio/nsc/pc97317/Makefile.inc

@@ -18,4 +18,5 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 ##
 
+romstage-$(CONFIG_SUPERIO_NSC_PC97317) += early_serial.c
 ramstage-$(CONFIG_SUPERIO_NSC_PC97317) += superio.c

src/superio/nsc/pc97317/early_serial.c

@@ -19,13 +19,15 @@
  */
 
 #include <arch/io.h>
+#include <device/pnp.h>
+#include <stdint.h>
 #include "pc97317.h"
 
 #define PM_DEV PNP_DEV(0x2e, PC97317_PM)
 #define PM_BASE 0xe8
 
 /* The PC97317 needs clocks to be set up before the serial port will operate. */
-static void pc97317_enable_serial(pnp_devfn_t dev, u16 iobase)
+void pc97317_enable_serial(pnp_devfn_t dev, u16 iobase)
 {
 	/* Set base address of power management unit. */
 	pnp_set_logical_device(PM_DEV);

src/superio/nsc/pc97317/pc97317.h

@@ -18,8 +18,8 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#ifndef SUPERIO_NSC_PC97317_PC97317_H
-#define SUPERIO_NSC_PC97317_PC97317_H
+#ifndef SUPERIO_NSC_PC97317_H
+#define SUPERIO_NSC_PC97317_H
 
 #define PC97317_KBCK 0x00 /* Keyboard */
 #define PC97317_KBCM 0x01 /* Mouse */
@@ -31,4 +31,9 @@
 #define PC97317_GPIO 0x07
 #define PC97317_PM   0x08 /* Power Management */
 
-#endif
+#include <arch/io.h>
+#include <stdint.h>
+
+void pc97317_enable_serial(pnp_devfn_t dev, u16 iobase);
+
+#endif /* SUPERIO_NSC_PC97317_H */

src/superio/nsc/pc97317/superio.c

@@ -28,7 +28,6 @@
 
 static void init(struct device *dev)
 {
-
 	if (!dev->enabled)
 		return;