runtime: remove systemstack logic from adjustframe

Remove logic for skipping some adjustframe logic for systemstack (aka
FuncID_systemstack_switch). This was introduced in 2014 by
9198ed4 but doesn't seem to be needed
anymore.

Updates #59692

Change-Id: I2368d64f9bb28ced4e7f15c9b15dac7a29194389
Reviewed-on: https://go-review.googlesource.com/c/go/+/489116
Reviewed-by: Michael Knyszek <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Felix Geisendörfer <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: felixge

src/runtime/stack.go

@@ -676,13 +676,6 @@ func adjustframe(frame *stkframe, adjinfo *adjustinfo) {
 		adjustpointer(adjinfo, unsafe.Pointer(frame.varp))
 	}
 
-	if f.funcID == abi.FuncID_systemstack_switch {
-		// A special routine at the bottom of stack of a goroutine that does a systemstack call.
-		// We will allow it to be copied even though we don't
-		// have full GC info for it (because it is written in asm).
-		return
-	}
-
 	locals, args, objs := frame.getStackMap(&adjinfo.cache, true)
 
 	// Adjust local variables if stack frame has been allocated.