x86/mm: Add missing comments for initial kernel direct mapping
x86/mm: Add missing comments for initial kernel direct mapping

Two sets of comments were lost during patch-series shuffling:

  - comments for init_range_memory_mapping()

  - comments in init_mem_mapping that is helpful for reminding people
    that the pagetable is setup top-down

The comments were written by Yinghai in his patch in:

   https://lkml.org/lkml/2012/11/28/620

This patch reintroduces them.

Originally-From: Yinghai Lu <0674548f4d596393408a51d6287a76ebba2f42aa@kernel.org>
Signed-off-by: Zhang Yanfei <534d7ac402faa9bfcaa7a720189a515766d4eb1f@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <9b26f769475fafc2d25107053b1bdd774d49438a@jp.fujitsu.com>
Cc: Konrad Rzeszutek Wilk <da3a51b335cef0eb0e2c329c5ef6bcd6acef687a@oracle.com>
Cc: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Link: b1d31715869dcc1f6a0ac3f659b7e2ac65f4e65b@gmail.com
[ Tidied it all up a bit. ]
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs