e2fsck: double cast a pointer to suppress a bogus compiler warning in kfree()

e2fsck: double cast a pointer to suppress a bogus compiler warning in kfree()

The C standard is wrong[1] with respect to the function signature of
free(), while the kernel's kfree() is correct.  Unfortunately, this
leads to compiler warnings.

Sayeth Dennis Ritchie: "Noalias must go.  This is non-negotiable"[2].
Noalias went.  The confusion around const, alas, still remains.

[1] https://yarchive.net/comp/const.html
[2] https://www.lysator.liu.se/c/dmr-on-noalias.html

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