realtek: dsa: rtl931x: downgrade print_matrix to debug

realtek: dsa: rtl931x: downgrade print_matrix to debug

Downgrade rtldsa_931x_print_matrix from pr_info to pr_debug to reduce
the massive amount printed during boot (64 lines). There doesn't seem
any benefit right now for keeping this at info level. And RTL931X is
the only variant that uses info-level print right now, all others
already use pr_debug.

Debug output can be activated individually for people who need this for
testing/debugging.

Link: https://github.com/openwrt/openwrt/pull/24507
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>