[gdb/testsuite] Fix clean_restart <absolute filename> in gdb.arch/aarch64*.exp

Fix clean_restart <absolute filename> in gdb.arch/aarch64*.exp.

Tested on aarch64-linux, M1 system.

There's a large number (44) of unsupported, for the following reasons:
- allow_aarch64_gcs_tests
- allow_aarch64_mops_tests
- allow_aarch64_sve_tests / target does not support SVE
- memory tagging unsupported

Consequently, we mostly use the simple substitution:
...
clean_restart $binfile
->
clean_restart
gdb_load $binfile
...