amd64_edac: cleanup f10_early_channel_count

Do not read DCLR[01] again since this is done in
amd64_read_mc_registers() earlier. There can be more than two physical
DIMMs present so clamp the channels value to max 2. Also, do not report
DCT data width - it is also done earlier.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>