[AF_PACKET]: Use void * for virtual addresses.

[AF_PACKET]: Use void * for virtual addresses.

I've been auditing code, cleaning up warning where code passes
unsigned long's to functions and macros that really take pointers.

Here's some explanation as to why I think these types were coded up
this way originally:
http://marc.theaimsgroup.com/?l=linux-mm&m=109155379124628&w=2

The attached patch make packet_opt->pg_vec a pointer to an array of
char*'s instead of a pointer to an array of unsigned