DEPS.xwalk: Roll v8-crosswalk (5b2efea -> 69921d6)

69921d6 Merge pull request #47 from vvavrychuk/simd-mips
75c28d9 [PATCH] fixed compilation v8 on mips

Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@globallogic.com>