arm: fix load ELF error leak

Spotted by ASAN:
QTEST_QEMU_BINARY=aarch64-softmmu/qemu-system-aarch64 tests/boot-serial-test

Direct leak of 48 byte(s) in 1 object(s) allocated from:
    #0 0x7ff8a9b0ca38 in __interceptor_calloc (/lib64/libasan.so.4+0xdea38)
    #1 0x7ff8a8ea7f75 in g_malloc0 ../glib/gmem.c:124
    #2 0x55fef3d99129 in error_setv /home/elmarco/src/qemu/util/error.c:59
    #3 0x55fef3d99738 in error_setg_internal /home/elmarco/src/qemu/util/error.c:95
    #4 0x55fef323acb2 in load_elf_hdr /home/elmarco/src/qemu/hw/core/loader.c:393
    #5 0x55fef2d15776 in arm_load_elf /home/elmarco/src/qemu/hw/arm/boot.c:830
    #6 0x55fef2d16d39 in arm_load_kernel_notify /home/elmarco/src/qemu/hw/arm/boot.c:1022
    #7 0x55fef3dc634d in notifier_list_notify /home/elmarco/src/qemu/util/notify.c:40
    #8 0x55fef2fc3182 in qemu_run_machine_init_done_notifiers /home/elmarco/src/qemu/vl.c:2716
    #9 0x55fef2fcbbd1 in main /home/elmarco/src/qemu/vl.c:4679
    #10 0x7ff89dfed009 in __libc_start_main (/lib64/libc.so.6+0x21009)

Signed-off-by: Marc-André Lureau <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>

hw/arm/boot.c

@@ -829,6 +829,7 @@ static uint64_t arm_load_elf(struct arm_boot_info *info, uint64_t *pentry,
 
     load_elf_hdr(info->kernel_filename, &elf_header, &elf_is64, &err);
     if (err) {
+        error_free(err);
         return ret;
     }