ext4: teach ext4_ext_find_extent() to realloc path if necessary

This adds additional safety in case for some reason we end reusing a
path structure which isn't big enough for current depth of the inode.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --cc fs/ext4/ext4_extents.h
Simple merge

diff --cc fs/ext4/extents.c
Simple merge