fix array index out of bound exception

Array index out of bound exception occurs when the 'part' variable is passed into the freeSpactTable array,
this can be avoided using pointer arithmetic.

Signed-off-by: F.A. SULAIMAN <asha.16@itfac.mrt.ac.lk>

fs/udf/super.c

@@ -2522,7 +2522,7 @@ static unsigned int udf_count_free(struct super_block *sb)
 			sbi->s_lvid_bh->b_data;
 		if (le32_to_cpu(lvid->numOfPartitions) > part) {
 			accum = le32_to_cpu(
-					lvid->freeSpaceTable[part]);
+					(lvid->freeSpaceTable + part));
 			if (accum == 0xFFFFFFFF)
 				accum = 0;
 		}