kernel/x86: Don't skip the first address when fetching user stack traces.

Let the loop handle the iframe instead of processing it up front,
so that it doesn't call get_next_frame_no_debugger the first time around.

Fixes the profiler skipping the first function when profiling user
space only.

src/system/kernel/arch/x86/arch_debug.cpp

@@ -1147,8 +1147,7 @@ arch_debug_get_stack_trace(addr_t* returnAddresses, int32 maxCount,
 		if (frame == NULL)
 			return 0;
 
-		bp = frame->bp;
+		bp = (addr_t)frame;
-		onKernelStack = false;
 	}
 
 	while (bp != 0 && count < maxCount) {