[fix] : increase serial baud rate to 115200

See archlinux/archiso@06c3218

Author: Hayao0819

syslinux/archiso_head.cfg

@@ -5,7 +5,7 @@
 # (c) 2019-2021 Fascode Network.
 #
 
-SERIAL 0 38400
+SERIAL 0 115200
 UI syslinux/vesamenu.c32
 MENU TITLE %OS_NAME%
 MENU BACKGROUND syslinux/splash.png
@@ -31,4 +31,4 @@ MENU COLOR timeout      1;37;40 #c0ffffff #00000000 std
 MENU COLOR msg07        37;40   #90ffffff #a0000000 std
 MENU COLOR tabmsg       31;40   #30ffffff #00000000 std
 
-MENU CLEAR
+MENU CLEAR