ISCSIUIO: Updated iscsiuio to version 0.7.8.1b for perf optimization

uIP v0.7.8.1b (May 01, 2013)
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   Enhancements
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   1. Change:  Performance optimization by caching the page size
      Impact:  All

   2. Change:  Fixed a bug in the tx completion interrupt handler
      Impact:  10G only

Signed-off-by: Eddie Wai <eddie.wai@broadcom.com>