kernel: start the semaphore wait timer after the early returns (#1173)

Wait() read the clock and looked up the thread id before checking for an available token. Both are only needed once the thread has to block.

src/kernel/semaphore.cpp

@@ -198,12 +198,6 @@ KernelSemaPrivate::Result KernelSemaPrivate::Wait(int need_count, uint32_t* ptr_
 		infinitely = false;
 	}
 
-	uint32_t      elapsed = 0;
-	Common::Timer t;
-	t.Start();
-
-	int id = Common::Thread::GetThreadIdUnique();
-
 	if (m_count >= need_count) {
 		m_count -= need_count;
 		if (ptr_micros != nullptr) {
@@ -216,6 +210,12 @@ KernelSemaPrivate::Result KernelSemaPrivate::Wait(int need_count, uint32_t* ptr_
 		return Result::TimedOut;
 	}
 
+	uint32_t      elapsed = 0;
+	Common::Timer t;
+	t.Start();
+
+	int id = Common::Thread::GetThreadIdUnique();
+
 	WaitingThread waiter {};
 	waiter.id         = id;
 	waiter.priority   = (m_fifo_order ? 0 : Libs::LibKernel::PthreadGetCurrentPriorityForKernel());