[LLD] [ELF] Add parentheses to silence a GCC warning. NFC.

This silences the following warning:

../tools/lld/ELF/SyntheticSections.cpp:1596:48: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
 1596 |   assert((index != 0 || type != target->gotRel && type != target->pltRel ||

Differential Revision: https://reviews.llvm.org/D127395