marvell firwmare: update 8897 PCIe firmware to 15.68.4.p7

Update 8897 uapsta firmware to 15.68.4.p7.

BUG=chrome-os-partner:25980
TEST=Manual: Boot, and ensure firmware revision is displayed.
Do a connect and idle test.

Change-Id: I5142575ecebd976f5527276974f2da468f1674c4
Reviewed-on: https://chromium-review.googlesource.com/187136
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Paul Stewart <pstew@chromium.org>
1 file changed