IB/uverbs: Move ib_access_flags and ib_read_counters_flags to uapi

These constants are used in the ioctl interface so they are part of the
uapi, place them in the correct header for clarity.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>