Limit the size of the posted receive buffers in Rx Rings to MJUMPAGESIZE. Previously for jumbo MTUs, the rx ring buffers were
MTU + any required pad. Now when this size greater than MJUMPAGESIZE, the packet is spanned across multiple buffers and the
mbufs are stiched together.

Submitted by:gary.zambrano@qlogic.com
Approved by:davidcs@freebsd.org