EDAC, Calxeda highbank: Convert to use simple_open()

This removes an open coded simple_open() function and replaces file
operations references to the function with simple_open() instead.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)

Cc: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>