perf tests test_arm_spe: Address shellcheck warnings about signal name case

perf tests test_arm_spe: Address shellcheck warnings about signal name case

Running shellcheck -S on test_arm_spe.sh throws below warnings:

 #shellcheck -S warning tests/shell/test_arm_spe.sh
In tests/shell/test_arm_spe.sh line 30:
trap cleanup_files exit term int
                   ^--^ SC3049 (warning): In POSIX sh, using lower/mixed case for signal names is undefined.
                        ^--^ SC3049 (warning): In POSIX sh, using lower/mixed case for signal names is undefined.
                             ^-^ SC3049 (warning): In POSIX sh, using lower/mixed case for signal names is undefined.

Fixed this issue by using uppercase for "EXIT", "TERM" and
"INIT" signals to avoid using lower/mixed case for signal
names as input.

Signed-off-by: Abhirup Deb <abhirupdeb@linux.vnet.ibm.com>
Cc: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20230613164145.50488-11-atrajeev@linux.vnet.ibm.com
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Mukesh Chaurasiya <mukesh.chaurasiya@ibm.com>
Signed-off-by: Ojaswin Mujoo <ojaswin.mujoo@ibm.com>
Signed-off-by: Piyush Sachdeva <Piyush.Sachdeva@ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>