malta: fix image prefix names

Signed-off-by: John Crispin <john@phrozen.org>

target/linux/malta/README

@@ -5,15 +5,15 @@ troubleshoot MIPS applications without access to real hardware.
 To use the images built by OpenWrt with qemu, use the following commands:
 
 For the 32 bit little-endian image:
-qemu-system-mipsel -kernel bin/targets/malta/le/lede-malta-le-vmlinux-initramfs.elf -nographic -m 256
+qemu-system-mipsel -kernel bin/targets/malta/le/openwrt-malta-le-vmlinux-initramfs.elf -nographic -m 256
 
 For the 32 bit big-endian image:
-qemu-system-mips -kernel bin/targets/malta/be/lede-malta-be-vmlinux-initramfs.elf -nographic -m 256
+qemu-system-mips -kernel bin/targets/malta/be/openwrt-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
+qemu-system-mips64el -kernel bin/targets/malta/le64/openwrt-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
+qemu-system-mips64 -kernel bin/targets/malta/be64/openwrt-malta-be64-vmlinux-initramfs.elf -nographic -m 256
 
 and enjoy the system bootin.