fuse2fs: fix punching post-EOF blocks during truncate

fuse2fs: fix punching post-EOF blocks during truncate

ext2fs_punch() can update the inode that's passed in, so we need to
write it back.  This should fix some fstests failures where the test
file system ends up with inodes where all extent records fit within the
inode but inexplicably have extents beyond EOF.  While we're at it, add
the fuse2fs prefix to the two helper functions.

Cc: linux-ext4@vger.kernel.org # v1.47.3
Fixes: 4581ac60eb53ec ("fuse2fs: fix post-EOF preallocation clearing on truncation")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20250726162848.GQ2672022@frogsfrogsfrogs
Signed-off-by: Theodore Ts'o <tytso@mit.edu>