docs: wrong path

docs/booting-openwrt-in-qemu-using-uboot-and-rustsbi.md

@@ -159,7 +159,7 @@ $ qemu-system-riscv64 \
 -bios ./u-boot/spl/u-boot-spl \
 -device virtio-net-device,netdev=eth0 -netdev user,id=eth0 \
 -device virtio-rng-pci -device ahci,id=ahci -device ide-hd,bus=ahci.0,drive=mydrive \
--drive file=./openwrt/openwrt-sifiveu-generic-sifive_unleashed-ext4-sdcard.img,format=raw,if=none,id=mydrive \
+-drive file=./openwrt-sifiveu-generic-sifive_unleashed-ext4-sdcard.img,format=raw,if=none,id=mydrive \
 -device loader,file=./u-boot/u-boot.itb,addr=0x80200000 \
 -device e1000,netdev=n1 -netdev user,id=n1,hostfwd=tcp::12055-:22
 ```