RDMA: Change all uapi headers to use __aligned_u64 instead of __u64

The new auditing standard for the subsystem will be to only use
__aligned_64 in uapi headers to try and prevent 32/64 compat bugs
from existing in the future.

Changing all existing usage will help ensure new developers copy the
right idea.

The before/after of this patch was tested using pahole on 32 and 64
bit compiles to confirm it has no change in the structure layout, so
this patch is a NOP.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>