x86/mce/amd, edac: Remove report_gart_errors

... because no one should be interested in spurious MCEs anyway. Make
the filtering unconditional and move it to amd_filter_mce().

Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200407163414.18058-2-bp@alien8.de