milkymist: Check for failure trying to load BIOS image

Check the return value from load_image_targphys(), which tells us
whether our attempt to load the BIOS image into RAM failed.
(Spotted by Coverity, CID 1190305.)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: NMichael Walle <michael@walle.cc>
Message-id: 20181030170032.1844-1-peter.maydell@linaro.org

hw/lm32/milkymist.c

@@ -138,7 +138,10 @@ milkymist_init(MachineState *machine)
     bios_filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
 
     if (bios_filename) {
-        load_image_targphys(bios_filename, BIOS_OFFSET, BIOS_SIZE);
+        if (load_image_targphys(bios_filename, BIOS_OFFSET, BIOS_SIZE) < 0) {
+            error_report("could not load bios '%s'", bios_filename);
+            exit(1);
+        }
     }
 
     reset_info->bootstrap_pc = BIOS_OFFSET;