fs: ext4: fix uninitialized symbols

fs: ext4: fix uninitialized symbols

Fix the issue detected by the smatch tool.

fs/ext4/inode.c:3583 ext4_map_blocks_atomic_write_slow() error: uninitialized symbol 'next_pblk'.
fs/ext4/namei.c:1776 ext4_lookup() error: uninitialized symbol 'de'.
fs/ext4/namei.c:1829 ext4_get_parent() error: uninitialized symbol 'de'.
fs/ext4/namei.c:3162 ext4_rmdir() error: uninitialized symbol 'de'.
fs/ext4/namei.c:3242 __ext4_unlink() error: uninitialized symbol 'de'.
fs/ext4/namei.c:3697 ext4_find_delete_entry() error: uninitialized symbol 'de'.

These changes enhance code clarity, address static analysis tool errors.

Signed-off-by: Ranganath V N <vnranganath.20@gmail.com>
Message-ID: <20251011063830.47485-1-vnranganath.20@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>