efi: return a value from sem_down()

GCC is rightly complaining that we aren't returning a value from
sem_down() like we should be,

efi/main.c: In function ‘sem_down’:
efi/main.c:174:1: warning: control reaches end of non-void function [-Wreturn-type]

It doesn't really matter what value we return because the return value
is only used in core/thread which EFI doesn't need.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/efi/main.c b/efi/main.c
index 5d71b398..727cfae0 100644
--- a/efi/main.c
+++ b/efi/main.c
@@ -172,6 +172,7 @@ struct semaphore;
 mstime_t sem_down(struct semaphore *sem, mstime_t time)
 {
 	/* EFI is single threaded */
+	return 0;
 }
 
 void sem_up(struct semaphore *sem)