fs: Rename mapping private members

fs: Rename mapping private members

It is hard to find where mapping->private_lock, mapping->private_list and
mapping->private_data are used, due to private_XXX being a relatively
common name for variables and structure members in the kernel.  To fit
with other members of struct address_space, rename them all to have an
i_ prefix.  Tested with an allmodconfig build.

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Acked-by: Darrick J. Wong <[email protected]>
Reviewed-by: Josef Bacik <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>