malta: add 64 bit qemu commands to README

This shows how to boot up the 64 bit images.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/malta/README

@@ -4,10 +4,16 @@ troubleshoot MIPS applications without access to real hardware.
 
 To use the images built by OpenWrt with qemu, use the following commands:
 
-For the little-endian image:
+For the 32 bit little-endian image:
 qemu-system-mipsel -kernel bin/targets/malta/le/lede-malta-le-vmlinux-initramfs.elf -nographic -m 256
 
-For the big-endian image:
+For the 32 bit big-endian image:
 qemu-system-mips -kernel bin/targets/malta/be/lede-malta-be-vmlinux-initramfs.elf -nographic -m 256
 
+For the 64 bit little-endian image:
+qemu-system-mips64el -kernel bin/targets/malta/le64/lede-malta-le64-vmlinux-initramfs.elf -nographic -m 256
+
+For the 64 bit big-endian image:
+qemu-system-mips64 -kernel bin/targets/malta/be64/lede-malta-be64-vmlinux-initramfs.elf -nographic -m 256
+
 and enjoy the system bootin.