exfat: initialize name_len

This compilation warning was observed using GCC 9:

  CC [M]  /home/arter97/linux-exfat/core_exfat.o
/home/arter97/linux-exfat/core_exfat.c: In function ‘exfat_find_dir_entry’:
/home/arter97/linux-exfat/core_exfat.c:737:19: warning: ‘name_len’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  737 |  s32 order, step, name_len;
      |                   ^~~~~~~~

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>

core_exfat.c

@@ -734,7 +734,7 @@ static s32 exfat_find_dir_entry(struct super_block *sb, FILE_ID_T *fid,
 		CHAIN_T *p_dir, UNI_NAME_T *p_uniname, s32 num_entries, DOS_NAME_T *unused, u32 type)
 {
 	s32 i, rewind = 0, dentry = 0, end_eidx = 0, num_ext = 0, len;
-	s32 order, step, name_len;
+	s32 order, step, name_len = 0;
 	s32 dentries_per_clu, num_empty = 0;
 	u32 entry_type;
 	u16 entry_uniname[16], *uniname = NULL, unichar;