kdump: add missing RAM resource in crash_shrink_memory()

kdump: add missing RAM resource in crash_shrink_memory()

When shrinking crashkernel memory using /sys/kernel/kexec_crash_size for
the newly added memory no RAM resource is created at the moment.

Example:

$ cat /proc/iomem
00000000-bfffffff : System RAM
  00000000-005b7ac3 : Kernel code
  005b7ac4-009743bf : Kernel data
  009bb000-00a85c33 : Kernel bss
c0000000-cfffffff : Crash kernel
d0000000-ffffffff : System RAM

$ echo 0 > /sys/kernel/kexec_crash_size
$ cat /proc/iomem
00000000-bfffffff : System RAM
  00000000-005b7ac3 : Kernel code
  005b7ac4-009743bf : Kernel data
  009bb000-00a85c33 : Kernel bss
                                 <<-- here is System RAM missing
d0000000-ffffffff : System RAM

One result of this bug is that the memory chunk can never be set offline
using memory hotplug.  With this patch I insert a new "System RAM"
resource for the released memory.  Then the upper example looks like the
following:

$ echo 0 > /sys/kernel/kexec_crash_size
$ cat /proc/iomem
00000000-bfffffff : System RAM
  00000000-005b7ac3 : Kernel code
  005b7ac4-009743bf : Kernel data
  009bb000-00a85c33 : Kernel bss
c0000000-cfffffff : System RAM   <<-- new rescoure
d0000000-ffffffff : System RAM

And now I can set chunk c0000000-cfffffff offline.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>