fs/fat/fat.c: fix warning: 'part_size' defined but not used

Commit c30a15e5 "FAT: Add FAT write feature" introduced a compiler
warning.  Fix this.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Donggeun Kim <dg77.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>

fs/fat/fat.c

@@ -46,7 +46,6 @@ static void downcase (char *str)
 static block_dev_desc_t *cur_dev = NULL;
 
 static unsigned long part_offset = 0;
-static unsigned long part_size;
 
 static int cur_part = 1;
 
@@ -100,7 +99,6 @@ int fat_register_device (block_dev_desc_t * dev_desc, int part_no)
 	if (!get_partition_info(dev_desc, part_no, &info)) {
 		part_offset = info.start;
 		cur_part = part_no;
-		part_size = info.size;
 	} else if ((strncmp((char *)&buffer[DOS_FS_TYPE_OFFSET], "FAT", 3) == 0) ||
 		   (strncmp((char *)&buffer[DOS_FS32_TYPE_OFFSET], "FAT32", 5) == 0)) {
 		/* ok, we assume we are on a PBR only */