ixgbevf: Fix unnecessary dereference where local var is available.

Remove dereference of hw pointer from adapter structure since a pointer
to the hw structure has already been allocated off the stack.  Also clean
up useless parenthesis.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>