fs/fcntl: use copy_to/from_user() for u64 types

Some architectures (at least PPC) doesn't like get/put_user with
64-bit types on a 32-bit system. Use the variably sized copy
to/from user variants instead.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: c75b1d94 ("fs: add fcntl() interface for setting/getting write life time hints")
Signed-off-by: Jens Axboe <axboe@kernel.dk>