netfs: fix up netfs_inode_init() docbook comment

netfs: fix up netfs_inode_init() docbook comment

Commit e81fb4198e27 ("netfs: Further cleanups after struct netfs_inode
wrapper introduced") changed the argument types and names, and actually
updated the comment too (although that was thanks to David Howells, not
me: my original patch only changed the code).

But the comment fixup didn't go quite far enough, and didn't change the
argument name in the comment, resulting in

  include/linux/netfs.h:314: warning: Function parameter or member 'ctx' not described in 'netfs_inode_init'
  include/linux/netfs.h:314: warning: Excess function parameter 'inode' description in 'netfs_inode_init'

during htmldoc generation.

Fixes: e81fb4198e27 ("netfs: Further cleanups after struct netfs_inode wrapper introduced")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>