base: Name segments after their index

base: Name segments after their index

Current loader is performing a linear scan of the section table for
every segment in the elf since it is naming every segment after the
sections it contains. With this patch we are just naming segments
after their index.
This is in any case how they are referenced when a readelf --segments
command is issued on the elf file.

Change-Id: I599400fcdfc0b80ac64632aba36781bd876777f0
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21999
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>