scripts/decode_stacktrace.sh: code: preserve alignment

With lines having a code to decode, the alignment was not preserved for
the first line.

With this sample ...

[ 52.238089][ T55] RIP: 0010:__ip_queue_xmit+0x127c/0x1820
[ 52.238401][ T55] Code: c1 83 e0 07 48 c1 e9 03 83 c0 03 (...)

... the script was producing the following output:

[ 52.238089][ T55] RIP: 0010:__ip_queue_xmit (...)
[ 52.238401][ T55] Code: c1 83 e0 07 48 c1 e9 03 83 c0 03 (...)

That's because scripts/decodecode doesn't preserve the alignment. No need
to modify it, it is enough to give only the "Code: (...)" part to this
script, and print the prefix without modifications.

With the same sample, we now have:

[ 52.238089][ T55] RIP: 0010:__ip_queue_xmit (...)
[ 52.238401][ T55] Code: c1 83 e0 07 48 c1 e9 03 83 c0 03 (...)

Link: https://lkml.kernel.org/r/20250908-decode_strace_indent-v1-3-28e5e4758080@kernel.org
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Tested-by: Carlos Llamas <cmllamas@google.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Elliot Berman <quic_eberman@quicinc.com>
Cc: Luca Ceresoli <luca.ceresoli@bootlin.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>