fs: convert most other generic_file_*mmap() users to .mmap_prepare()

fs: convert most other generic_file_*mmap() users to .mmap_prepare()

Update nearly all generic_file_mmap() and generic_file_readonly_mmap()
callers to use generic_file_mmap_prepare() and
generic_file_readonly_mmap_prepare() respectively.

We update blkdev, 9p, afs, erofs, ext2, nfs, ntfs3, smb, ubifs and vboxsf
file systems this way.

Remaining users we cannot yet update are ecryptfs, fuse and cramfs. The
former two are nested file systems that must support any underlying file
ssytem, and cramfs inserts a mixed mapping which currently requires a VMA.

Once all file systems have been converted to mmap_prepare(), we can then
update nested file systems.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/08db85970d89b17a995d2cffae96fb4cc462377f.1750099179.git.lorenzo.stoakes@oracle.com
Signed-off-by: Christian Brauner <brauner@kernel.org>