tunefs: Don't lower WARNS

Use casts to silence the alignment warnings instead of potentially
suppressing other legitimate warnings.

MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D56033

sbin/tunefs/Makefile

@@ -3,6 +3,4 @@ PROG=	tunefs
 LIBADD=	ufs util
 MAN=	tunefs.8
 
-WARNS?=	3
-
 .include <bsd.prog.mk>

sbin/tunefs/tunefs.c

@@ -640,7 +640,7 @@ dir_search(ufs2_daddr_t blk, int bytes)
 		return (-1);
 	}
 	for (off = 0; off < bytes; off += dp->d_reclen) {
-		dp = (struct direct *)&block[off];
+		dp = (struct direct *)(uintptr_t)&block[off];
 		if (dp->d_reclen == 0)
 			break;
 		if (dp->d_ino == 0)
@@ -705,7 +705,7 @@ dir_clear_block(const char *block, off_t off)
 	struct direct *dp;
 
 	for (; off < sblock.fs_bsize; off += DIRBLKSIZ) {
-		dp = (struct direct *)&block[off];
+		dp = (struct direct *)(uintptr_t)&block[off];
 		dp->d_ino = 0;
 		dp->d_reclen = DIRBLKSIZ;
 		dp->d_type = DT_UNKNOWN;
@@ -728,7 +728,7 @@ dir_insert(ufs2_daddr_t blk, off_t off, ino_t ino)
 		return (-1);
 	}
 	bzero(&block[off], sblock.fs_bsize - off);
-	dp = (struct direct *)&block[off];
+	dp = (struct direct *)(uintptr_t)&block[off];
 	dp->d_ino = ino;
 	dp->d_reclen = DIRBLKSIZ;
 	dp->d_type = DT_REG;