ixgbe: Drop check for PAGE_SIZE from ixgbe_xmit_frame_ring

The check for PAGE_SIZE is pointless now that the default configuration is to
allocate 32K for all buffers.  Since the Tx descriptor limit is 16K we can
just drop the check and always compare the descriptors to the maximum size
supported.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>