Update docs to use default XFS inode size

In past couple of years, the XFS team has greatly improved inode use in
xfs.  With more recent kernels, there is no performance penalty for
using the default inode size, and a smaller inode size gives us
improvements in other areas where disk access is involved.

DocImpact

Change-Id: Ie9da53a6e8bf43d1d02881befbb52595462c9f2e
Merge "Update docs to use default XFS inode size"