ixgbe: Don't call kmap() on page allocated with GFP_ATOMIC

Pages allocated with GFP_ATOMIC cannot come from Highmem. This is why
there is no need to call kmap() on them.

Therefore, don't call kmap() on rx_buffer->page() and instead use a
plain page_address() to get the kernel address.

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>