mfd: cros_ec: Export needed symbols for the i2c and spi modules

In order to fix those, when all cros code is modular:

ERROR: "cros_ec_prepare_tx" [drivers/mfd/cros_ec_spi.ko] undefined!
ERROR: "cros_ec_register" [drivers/mfd/cros_ec_spi.ko] undefined!
ERROR: "cros_ec_remove" [drivers/mfd/cros_ec_spi.ko] undefined!
ERROR: "cros_ec_suspend" [drivers/mfd/cros_ec_spi.ko] undefined!
ERROR: "cros_ec_resume" [drivers/mfd/cros_ec_spi.ko] undefined!
ERROR: "cros_ec_register" [drivers/mfd/cros_ec_i2c.ko] undefined!
ERROR: "cros_ec_remove" [drivers/mfd/cros_ec_i2c.ko] undefined!
ERROR: "cros_ec_suspend" [drivers/mfd/cros_ec_i2c.ko] undefined!
ERROR: "cros_ec_resume" [drivers/mfd/cros_ec_i2c.ko] undefined!

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/cros_ec.c

@@ -19,6 +19,7 @@
 
 #include <linux/interrupt.h>
 #include <linux/slab.h>
+#include <linux/module.h>
 #include <linux/mfd/core.h>
 #include <linux/mfd/cros_ec.h>
 #include <linux/mfd/cros_ec_commands.h>
@@ -41,6 +42,7 @@ int cros_ec_prepare_tx(struct cros_ec_device *ec_dev,
 
 	return EC_MSG_TX_PROTO_BYTES + msg->out_len;
 }
+EXPORT_SYMBOL(cros_ec_prepare_tx);
 
 static int cros_ec_command_sendrecv(struct cros_ec_device *ec_dev,
 		uint16_t cmd, void *out_buf, int out_len,
@@ -150,6 +152,7 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
 fail_din:
 	return err;
 }
+EXPORT_SYMBOL(cros_ec_register);
 
 int cros_ec_remove(struct cros_ec_device *ec_dev)
 {
@@ -160,6 +163,7 @@ int cros_ec_remove(struct cros_ec_device *ec_dev)
 
 	return 0;
 }
+EXPORT_SYMBOL(cros_ec_remove);
 
 #ifdef CONFIG_PM_SLEEP
 int cros_ec_suspend(struct cros_ec_device *ec_dev)
@@ -174,6 +178,7 @@ int cros_ec_suspend(struct cros_ec_device *ec_dev)
 
 	return 0;
 }
+EXPORT_SYMBOL(cros_ec_suspend);
 
 int cros_ec_resume(struct cros_ec_device *ec_dev)
 {
@@ -186,4 +191,6 @@ int cros_ec_resume(struct cros_ec_device *ec_dev)
 
 	return 0;
 }
+EXPORT_SYMBOL(cros_ec_resume);
+
 #endif