opae: bump revision to 2.8.0

[coveralls]

Pull Request Test Coverage Report for Build 5755446942

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 15 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.06%) to 73.553%

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Files with Coverage Reduction	New Missed Lines	%
libraries/plugins/xfpga/open.c	1	74.68%
libraries/plugins/uio/opae_uio.c	4	90.18%
libraries/plugins/vfio/opae_vfio.c	4	85.13%
libraries/plugins/xfpga/mmio.c	6	82.87%
<!--	Total:	15		-->

Totals
Change from base Build 5752925062:	-0.06%
Covered Lines:	15719
Relevant Lines:	21371

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💛 - Coveralls