[ELF] - Fixed crash in GnuHashTableSection.
[ELF] - Fixed crash in GnuHashTableSection.

r296570 intorduced crash revealed by 
gnu-hash-table.s which crashed for me.

Reason was use of uninitialized NBuckets variable.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@296597 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld