EDAC/mc_sysfs: Print MC-scope sysfs counters unsigned

This is cosmetically nicer for counts > INT32_MAX, and aligns the
MC-scope format with that of the lower layer sysfs counter files.

Signed-off-by: Eric Badger <ebadger@purestorage.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20211003181653.GA685515@ebadger-ThinkPad-T590