xfs: make the calculation generic in xfs_sb_validate_fsb_count()

xfs: make the calculation generic in xfs_sb_validate_fsb_count()

Instead of assuming that PAGE_SHIFT is always higher than the blocklog,
make the calculation generic so that page cache count can be calculated
correctly for LBS.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/r/20240822135018.1931258-10-kernel@pankajraghav.com
Acked-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>