tty: n_gsm: Remove unnecessary test in gsm_print_packet()

If the length is zero then the print_hex_dump_bytes won't output
anything, so testing the length before the call is unnecessary.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Link: https://lore.kernel.org/r/20200518084517.2173242-2-gregory.clement@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_gsm.c

@@ -504,7 +504,6 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
 	else
 		pr_cont("(F)");
 
-	if (dlen)
 	print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
 }