amd64_edac: make DRAM regions output more human-readable

Do not shift the TOP_MEM and TOP_MEM2 values by 23 but rather save the
whole 64-bit value read from the MSR. Although the TOP_MEM/TOP_MEM2 bits
are only a subset of the 64bit register, the values are correct since
the remaining bits are Read-As-Zero and no shifting is needed.

Also, cleanup DRAM base/limit debug output.

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