xfs: declare xfs_file.c symbols in xfs_file.h

xfs: declare xfs_file.c symbols in xfs_file.h

[ Upstream commit 00acb28d96746f78389f23a7b5309a917b45c12f ]

Move the two public symbols in xfs_file.c to xfs_file.h.  We're about to
add more public symbols in that source file, so let's finally create the
header file.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>