s390/ipl: Fix error path on BIOS loading

commit 18674b26
(elf-loader: add more return codes) enabled the elf loader to return
other errors than -1.

Lets also handle that case for our "BIOS" on s390.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
CC: Alexey Kardashevskiy <aik@ozlabs.ru>
CC: Alexander Graf <agraf@suse.de>

hw/s390x/ipl.c

@@ -80,7 +80,7 @@ static int s390_ipl_init(SysBusDevice *dev)
 
         bios_size = load_elf(bios_filename, NULL, NULL, &ipl->start_addr, NULL,
                              NULL, 1, ELF_MACHINE, 0);
-        if (bios_size == -1) {
+        if (bios_size < 0) {
             bios_size = load_image_targphys(bios_filename, ZIPL_IMAGE_START,
                                             4096);
             ipl->start_addr = ZIPL_IMAGE_START;