ext4: use local variable ei instead of EXT4_I() macro

Signed-off-by: chenyichong <chenyichong@uniontech.com>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/20210526052930.11278-1-chenyichong@uniontech.com


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