arm: relocate_code() is no longer noreturn

arm: relocate_code() is no longer noreturn

Commit e05e5de7fae5bec79617e113916dac6631251156 made ARM's relocate_code()
return to its caller, but it did not update its declaration accordingly.

Fixing this function declaration fixes dropped C code following calls to
relocate_code().

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>