configs: Using VExpress_GEM5_V1 as a default for Options.py

configs: Using VExpress_GEM5_V1 as a default for Options.py

This is replacing deprecated VExpress_EMM for scripts using Options.py,
like fs.py.

Change-Id: I2ba01b248bb9baf49e1f2217d623f3b9bc8a35f9
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25183
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>