riscv: roms: Fix make rules for building sifive_u bios

Currently the make rules are wrongly using qemu/virt opensbi image
for sifive_u machine. Correct it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Chih-Min Chao <chihmin.chao@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 1564812484-20385-1-git-send-email-bmeng.cn@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

roms/Makefile

@@ -183,7 +183,7 @@ opensbi64-sifive_u:
 	$(MAKE) -C opensbi \
 		CROSS_COMPILE=$(riscv64_cross_prefix) \
 		PLATFORM="qemu/sifive_u"
-	cp opensbi/build/platform/qemu/virt/firmware/fw_jump.bin ../pc-bios/opensbi-riscv64-sifive_u-fw_jump.bin
+	cp opensbi/build/platform/qemu/sifive_u/firmware/fw_jump.bin ../pc-bios/opensbi-riscv64-sifive_u-fw_jump.bin
 
 clean:
 	rm -rf seabios/.config seabios/out seabios/builds