[ELF] - Eliminate dead code from shouldKeepInSymtab. NFC.
[ELF] - Eliminate dead code from shouldKeepInSymtab. NFC.

shouldKeepInSymtab is called from copyLocalSymbols:
https://github.com/llvm-mirror/lld/blob/master/ELF/Writer.cpp#L574

The pre-condition is that symbol should be Defined:
https://github.com/llvm-mirror/lld/blob/master/ELF/Writer.cpp#L572

And its section is Live:
https://github.com/llvm-mirror/lld/blob/master/ELF/Writer.cpp#L548

InputSection::Discarded section can never be Live. And hence I believe
check I removed in this patch is excessive.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@335973 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld