mainboard/google/reef: declare mainboard_ec_init() in each C file

There's no common EC header file in the code base, and I didn't
want to use a header file for single declaration. Therefore,
just move the declaration to each file that uses that symbol.

BUG=chrome-os-partner:56677

Change-Id: Ibaebb0ea6a07029aec02d5185cf05ffb8593b117
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16420
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

src/mainboard/google/reef/bootblock.c

@@ -19,6 +19,8 @@
 #include <soc/gpio.h>
 #include <variant/ec.h>
 
+void mainboard_ec_init(void);
+
 void bootblock_mainboard_init(void)
 {
 	const struct pad_config *pads;

src/mainboard/google/reef/ec.c

@@ -20,6 +20,8 @@
 #include <soc/lpc.h>
 #include <variant/ec.h>
 
+void mainboard_ec_init(void);
+
 static void ramstage_ec_init(void)
 {
 	printk(BIOS_ERR, "mainboard: EC init\n");

src/mainboard/google/reef/mainboard.c

@@ -25,6 +25,8 @@
 #include <variant/ec.h>
 #include <variant/gpio.h>
 
+void mainboard_ec_init(void);
+
 static void mainboard_init(void *chip_info)
 {
 	int boardid;

src/mainboard/google/reef/variants/baseboard/include/baseboard/ec.h

@@ -70,8 +70,4 @@
 	 EC_HOST_EVENT_MASK(EC_HOST_EVENT_BATTERY_SHUTDOWN)|\
 	 EC_HOST_EVENT_MASK(EC_HOST_EVENT_PANIC))
 
-#ifndef __ACPI__
-extern void mainboard_ec_init(void);
-#endif
-
 #endif