mlx4_vnic: Add correct typecasting to pointers in vnic_get_frag_header()

mlx4_vnic: Add correct typecasting to pointers in vnic_get_frag_header()

The *mac_hdr (Mac Header) pointer should be incremented ETH_HLEN
bytes to get the *ip_hdr (IP Header) pointer. Similarly, the IP
Header pointer should be incremented by (iph->ihl << 2) bytes
to get the *tcpudp_hdr (Transport Header) pointer.

Fix this by adding a u8* cast to the two pointers while doing
the pointer arithmetic.

Orabug: 19824501

Signed-off-by: Ashish Samant <ashish.samant@oracle.com>
Acked-by: Rama Nichanamatlu <rama.nichanamatlu@oracle.com>
Signed-off-by: Guangyu Sun <guangyu.sun@oracle.com>