[ELF,test] eh-frame-hdr-sdata8.s: use AT() to avoid huge PT_LOAD segments
Use AT() to ensure output sections with huge addresses are placed in separate
PT_LOAD segments. Without this, 2.lds and 3.lds created a huge PT_LOAD
segment, making the sparse file size larger than 4GiB, unsupported by
some 32-bit systems.
https://github.com/llvm/llvm-project/pull/179089#issuecomment-3908549089