system-arm: Rename ARM bootloader directories

The patch is renaming:

system/arm/simple_bootloader -> system/arm/bootloader/arm
system/arm/aarch64_bootloader -> system/arm/bootloader/arm64

Change-Id: Ia7380be3914e277624060f1c96361a0f16dbea9d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Adrian Herrera <adrian.herrera@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23948
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
6 files changed