Update mem_dist.sh

Sample Output:

    [root@torroise tests]# ./mem_dist.sh

    Mem used in SLUB: 297.545MB    Total

    Mem used in Vmalloc: 290.188MB    Total

    Mem available in DMA buddy zone : 3 MB
    Mem available in DMA32 buddy zone : 307 MB
    Mem available in Normal buddy zone : 53 MB
    Total Mem available in all buddy zones : 363 MB

    [root@tortoise tests]#