[Assembler] Fix crash when assembling .quad for AArch32.

A 64-bit relocation does not exist in 32-bit ARMELF. Report an error
instead of crashing.

PR23870
Patch by Sanne Wouda (sanwou01).
Differential Revision: https://reviews.llvm.org/D28851

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292373 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed