Initialize reglocs for VMCOREINFO

Initialize reglocs for VMCOREINFO

MSan complains:

    Uninitialized value was created by an allocation of 'reglocs' in the stack frame
       #0 0x562d35c686f0 in handle_core_note elfutils/src/readelf.c:12674:3
       #const Ebl_Register_Location *reglocs;
    ==1006199==WARNING: MemorySanitizer: use-of-uninitialized-value
       #0 0x562d35c68a2a in handle_core_note elfutils/src/readelf.c:12692:11
       #colno = handle_core_registers (ebl, ebl->elf, desc + regs_offset,
       #                               reglocs, nregloc);

Strictly speaking, this is not a problem, because nregloc == 0, but for
other note types we initialize it anyway, so do it here as well.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>