ixgbe: Only use double buffering if page size is less than 8K

ixgbe: Only use double buffering if page size is less than 8K

This change makes it so that we do not use double buffering if the page
size is larger than 4K.  Instead we will simply walk through the page using
up to 3K per receive, and if we receive less than we only move the offset
by that amount.  We will free the page when there is no longer any space
left that we can use instead of checking the page count to see if we can
cycle back to the start.

The main motivation behind this is to avoid the unnecessary truesize cost
for using a half page when most packets are 2K or smaller. With this new
approach the largest possible truesize for a page fragment will be 3K when
PAGE_SIZE is larger than 4K.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>