scan-lto-assembler was looking for the old dump names instead of
the new ones. There are only two uses of this:
gcc.target/nios2/custom-fp-lto.c
gcc.target/aarch64/pr70044.c
Both of them use single source files, so I think they both want
the same behaviour.
gcc/testsuite/
* lib/scanasm.exp (scan-lto-assembler): Update expected name
of dump file.
