lib/pwauth.c: Remove dead code

lib/pwauth.c: Remove dead code

There are no users of 'clear_pass' and 'wipe_clear_pass'.

$ grep -rn '\<clear_pass\>'
lib/pwauth.c:35:/*@null@*/char *clear_pass = NULL;
lib/pwauth.c:199:	 * not wipe it (the caller should wipe clear_pass when it is
lib/pwauth.c:203:	clear_pass = clear;

$ grep -rn wipe_clear_pass
lib/pwauth.c:34:bool wipe_clear_pass = true;
lib/pwauth.c:198:	 * if the external variable wipe_clear_pass is zero, we will
lib/pwauth.c:204:	if (wipe_clear_pass && (NULL != clear) && ('\0' != *clear)) {
ChangeLog:3813:	* lib/pwauth.c: Use a boolean for wipe_clear_pass and use_skey.

Remove them.

Signed-off-by: Alejandro Colomar <alx@kernel.org>