x86: overmapped fix when 4K pages on tail, 64-bit

fix phys_pmd_init to make sure not to return bigger value than end.

also print out range split:1G/2M/4K in init_memory_mapping().

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>