[Artful/Bionic] [Config] enable EDAC_GHES for ARM64

[Manoj Iyer]

Please consider this patch to enable CONFIG_EDAC_GHES option for ARM64 in 
Artful and Bionic, so that the memory errors are processed and reported to 
the user space. This fixes the bug 
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1747746

A test kernel is available in PPA: 
https://launchpad.net/~centriq-team/+archive/ubuntu/lp1747746 
and was tested by me on QTI ARM64 QDF2400 platform. I also tested this 
on Power8 to check for any regressions. Test results are documented in the 
bug report.