bpf: Simplify character output in seq_print_delegate_opts()

Single characters should be put into a sequence.
Thus use the corresponding function “seq_putc” for two selected calls.

This issue was transformed by using the Coccinelle software.

Suggested-by: Christophe Jaillet <christophe.jaillet@wanadoo.fr>
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/abde0992-3d71-44d2-ab27-75b382933a22@web.de