Fix various small issues in the documentation ...

Change some hard-to-convert constructs to cleaner ones.
Fix a broken link.

Change-Id: Ida70aa1da0af7a107b0e05eb20b8d46669a0380b
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

hikey960: add document ...

Add document on HiKey960 platform and how to build.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>