fastboot: Refactor fastboot_okay/fail to take response

Add the response string as a parameter to fastboot_okay/fail, instead
of modifying a global, to match the contract expected by the AOSP
U-Boot code.

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/include/fastboot.h b/include/fastboot.h
index 009f1a7..ed52dae 100644
--- a/include/fastboot.h
+++ b/include/fastboot.h
@@ -15,7 +15,7 @@
 /* The 64 defined bytes plus \0 */
 #define FASTBOOT_RESPONSE_LEN	(64 + 1)
 
-void fastboot_fail(const char *reason);
-void fastboot_okay(const char *reason);
+void fastboot_fail(const char *reason, char *response);
+void fastboot_okay(const char *reason, char *response);
 
 #endif /* _FASTBOOT_H_ */