exfat: remove unnecessary reassignment of p_uniname->name_len

kbuild test robot reported :

	fs/exfat/nls.c:531:22: warning: Variable 'p_uniname->name_len'
	is reassigned a value before the old one has been used.

The reassignment of p_uniname->name_len is not needed and remove it.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/exfat/nls.c

@@ -514,8 +514,6 @@ static int exfat_utf8_to_utf16(struct super_block *sb,
 		return -ENAMETOOLONG;
 	}
 
-	p_uniname->name_len = unilen & 0xFF;
-
 	for (i = 0; i < unilen; i++) {
 		if (*uniname < 0x0020 ||
 		    exfat_wstrchr(bad_uni_chars, *uniname))