i2c: hix5hd2: add COMPILE_TEST

Commit 9439eb3a

 ("asm-generic: io: implement relaxed
accessor macros as conditional wrappers") has added
{read,write}{b,w,l,q}_relaxed to include/asm-generic/io.h.
So COMPILE_TEST can be added.

Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>