bnx2x: avoid two atomic ops per page on x86

Commit 4cace675 ("bnx2x: Alloc 4k fragment for each rx ring buffer
element") added extra put_page() and get_page() calls on arches where
PAGE_SIZE=4K like x86

Reorder things to avoid this overhead.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Cc: Yuval Mintz <Yuval.Mintz@cavium.com>
Cc: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>