ext4: use BUG_ON instead of if condition followed by BUG

BUG_ON would be better.

This issue was detected with the help of Coccinelle.
Reported-by: Zeal robot <zealci@zte.com.cn>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Link: https://lore.kernel.org/r/20211228073252.580296-1-xu.xin16@zte.com.cnSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -2400,8 +2400,7 @@ ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize)
 
 static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
 {
-	if ((len > blocksize) || (blocksize > (1 << 18)) || (len & 3))
-		BUG();
+	BUG_ON((len > blocksize) || (blocksize > (1 << 18)) || (len & 3));
 #if (PAGE_SIZE >= 65536)
 	if (len < 65536)
 		return cpu_to_le16(len);