Disable CONFIG_TMPFS_INODE64 which is currently broken on s390x
because size of ino_t on s390x is 4 bytes.

This fixes the following error with kdump:

[    9.415082] [608]: Remounting '/' read-only in with options 'size=238372k,nr_inodes=59593,inode64'.
[    9.415093] rootfs: Cannot use inode64 with <64bit inums in kernel
[    9.415093]
[    9.415100] [608]: Failed to remount '/' read-only: Invalid argument

Fixes: 5c60ed28 ("s390: update defconfigs")
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>