[dv] Fix name of ELF file in report
[dv] Fix name of ELF file in report

The name of the ELF file was wrong in the regr.log file, it should be
e.g. `riscv_debug_ebreakmu_test_9.o`, not
`riscv_debug_ebreakmu_test.9.o`.

AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex