xfs_db: write command broken on 64 bit values

xfs_db: write command broken on 64 bit values

convert_args() has problesm with 64 bit fields because it tries to
shift them by 64 bits. The result of doing so is undefined by the C
standard, and so results in the unexpected behaviour of the result
being being the original value unchanged rather than 0. Hence you
can't write 64 bit fields because the code thinks that all values
other than 0 are out of range.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>