explicitly zeroing elements. * grub-core/io/gzio.c (grub_gzio_open): Likewise. * grub-core/io/lzopio.c (grub_lzopio_open): Remove explicit zeroing of elements in a structure already allocated using grub_zalloc. * grub-core/io/xzio.c (grub_xzio_open): Likewise.