viogpu_queue: rearrange virtio_gpu_vbuffer struct to reduce size by 8 bytes

[sharkautarch]

Signed-off-by: sharkautarch [email protected]

Note that this change only makes a difference for x86_64 and ARM64 targets; the size of the struct will remain the same for x86.

This struct isn't packed, so padding/alignment of each member can increase the size. Reduces size of the struct from 72 bytes to 64 bytes. tested in godbolt: https://godbolt.org/z/M7abMvYhh

Rearrangement is based off of the idea of ordering the members of a struct from biggest to smallest. (I learned about that trick from a comment in this video about padding/alignment: https://www.youtube.com/watch?v=E0QhZ6tNoRg)

EDIT: I just realized that u32 is actually unsigned long (defined in VirtIO/linux/types.h), but it is still only 32 bits (same size as unsigned int because apparently long is 32 bits on 64bit windows). which I guess is why it is called u32 updated godbolt: https://godbolt.org/z/ffeGh4nvT clang now prints out 72 bytes for both, but the assembly for msvc x64 shows that the size is still reduced to 64 bytes