libblkid: topology/ioctl: correctly handle kernel types

libblkid: topology/ioctl: correctly handle kernel types

Commit 5d71d711d07a ("libblkid: topolicy/ioctl: use union for multiple data types")
incorrectly assumed that set_ulong and set_int refer to the type
returned by the kernel. Instead the different function pointer names
refer to the types of the function pointers.
However all ioctls, except for the later added BLKGETDISKSEQ, return
32bit integers.
This made libblkid also interpret the upper 32bits too, leading to
garbage values.

Introduce a new member 'kernel_size' to also handle the 64bit
BLKGETDISKSEQ.

Drop data.ul as it is no actually used.

Closes #2904
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>