ext4: remove unused assignments

ext4: remove unused assignments

The eh assignment in these two places is meaningless, because the
function will goto to merge, which will not use eh.

The clang_analyzer complains as follows:

fs/ext4/extents.c:1988:4 warning:
fs/ext4/extents.c:2016:4 warning:

Value stored to 'eh' is never read

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: luo penghao <luo.penghao@zte.com.cn>
Link: https://lore.kernel.org/r/20211104064007.2919-1-luo.penghao@zte.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>