[Object] Remove check for BIND_OPCODE_DONE/REBASE_OPCODE_DONE.

BIND_OPCODE_DONE/REBASE_OPCODE_DONE may appear at the end of the opcode array,
but they are not required to. The linker only adds them as padding to align the
opcodes to pointer size.

This fixes rdar://problem/31285560.

llvm-svn: 299104