ext4: use kmalloc_array() for array space allocation

Replace kmalloc(size * sizeof) with kmalloc_array() for safer memory
allocation and overflow prevention.

Cc: stable@kernel.org
Signed-off-by: Liao Yuanhong <liaoyuanhong@vivo.com>
Link: https://patch.msgid.link/20250811125816.570142-1-liaoyuanhong@vivo.com


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