[ELF] - Eliminate dead "if". NFC.

We call switchTo() from assignAddresses() for switching to Aether,
and from assignOffsets().

First calls assignOffsets() one by one for each output section.
(https://github.com/llvm-mirror/lld/blob/master/ELF/LinkerScript.cpp#L1045)

That I believe means the condition removed in this patch is dead.

llvm-svn: 336356

lld/ELF/LinkerScript.cpp

@@ -710,8 +710,6 @@ void LinkerScript::output(InputSection *S) {
 }
 
 void LinkerScript::switchTo(OutputSection *Sec) {
-  if (Ctx->OutSec == Sec)
-    return;
   Ctx->OutSec = Sec;
 
   uint64_t Before = advance(0, 1);