S2IO: Checking for the return value of pci map function

 - Checking for the return value of pci map function
 - Implemented Francois Romieu's comments on eliminating code duplication
   using goto
 - Implemented Francois Romieu's comments on using a temporary variable for
   accessing statistics structure

Signed-off-by: Veena Parat <veena.parat@neterion.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>