vxge: Fixed crash in PAE system due to wrong typecasting.

- Fix a crash in PAE system due to wrong typecasting.

- On PAE system size_t is unsigned int which is 32bit. Avoid casting
  64 bit address to 32 bit

Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@neterion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>