[grub]: allow access from both console and serial (sonic-net#4444)

console means the vga port. this is mainly used for virtual environment such as hyper-v or virtualbox where you have the virtual vga port to display the boot up process.

Signed-off-by: Guohan Lu <[email protected]>

installer/x86_64/install.sh

@@ -545,8 +545,8 @@ export GRUB_CMDLINE_LINUX
 # Add common configuration, like the timeout and serial console.
 cat <<EOF > $grub_cfg
 $GRUB_SERIAL_COMMAND
-terminal_input serial
-terminal_output serial
+terminal_input console serial
+terminal_output console serial
 
 set timeout=5