tty: n_gsm: Fix packet data hex dump output

tty: n_gsm: Fix packet data hex dump output

commit 925ea0fa5277c1e6bb9e51955ef34eea9736c3d7 upstream.

The module param debug for n_gsm uses KERN_INFO level, but the hexdump
now uses KERN_DEBUG level. This started after commit 091cb0994edd
("lib/hexdump: make print_hex_dump_bytes() a nop on !DEBUG builds").
We now use dynamic_hex_dump() unless DEBUG is set.

This causes no packets to be seen with modprobe n_gsm debug=0x1f unlike
earlier. Let's fix this by adding gsm_hex_dump_bytes() that calls
print_hex_dump() with KERN_INFO to match what n_gsm is doing with the
other debug related output.

Fixes: 091cb0994edd ("lib/hexdump: make print_hex_dump_bytes() a nop on !DEBUG builds")
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20220512131506.1216-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>