Cleanup of SDL_SetError that already return -1 value

src/thread/ngage/SDL_sysmutex.cpp

@@ -92,8 +92,7 @@ SDL_LockMutex(SDL_mutex * mutex)
 {
     if (mutex == NULL)
     {
-        SDL_SetError("Passed a NULL mutex.");
-        return -1;
+        return SDL_SetError("Passed a NULL mutex.");
     }
 
     RMutex rmutex;
@@ -109,8 +108,7 @@ SDL_UnlockMutex(SDL_mutex * mutex)
 {
     if ( mutex == NULL )
     {
-        SDL_SetError("Passed a NULL mutex.");
-        return -1;
+        return SDL_SetError("Passed a NULL mutex.");
     }
 
     RMutex rmutex;

src/thread/ngage/SDL_syssem.cpp

@@ -119,8 +119,7 @@ SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
 {
     if (! sem)
     {
-        SDL_SetError("Passed a NULL sem");
-        return -1;
+        return SDL_SetError("Passed a NULL sem");
     }
 
     if (timeout == SDL_MUTEX_MAXWAIT)
@@ -182,8 +181,7 @@ SDL_SemPost(SDL_sem * sem)
 {
     if (! sem)
     {
-        SDL_SetError("Passed a NULL sem.");
-        return -1;
+        return SDL_SetError("Passed a NULL sem.");
     }
     sem->count++;
     RSemaphore sema;