powerpc/pseries/memhotplug: Quieten some DLPAR operations

powerpc/pseries/memhotplug: Quieten some DLPAR operations

When attempting to remove by index a set of LMBs a lot of messages are
displayed on the console, even when everything goes fine:

  pseries-hotplug-mem: Attempting to hot-remove LMB, drc index 8000002d
  Offlined Pages 4096
  pseries-hotplug-mem: Memory at 2d0000000 was hot-removed

The 2 messages prefixed by "pseries-hotplug-mem" are not really
helpful for the end user, they should be debug outputs.

In case of error, because some of the LMB's pages couldn't be
offlined, the following is displayed on the console:

  pseries-hotplug-mem: Attempting to hot-remove LMB, drc index 8000003e
  pseries-hotplug-mem: Failed to hot-remove memory at 3e0000000
  dlpar: Could not handle DLPAR request "memory remove index 0x8000003e"

Again, the 2 messages prefixed by "pseries-hotplug-mem" are useless,
and the generic DLPAR prefixed message should be enough.

These 2 first changes are mainly triggered by the changes introduced
in drmgr:
  https://groups.google.com/g/powerpc-utils-devel/c/Y6ef4NB3EzM/m/9cu5JHRxAQAJ

Also, when adding a bunch of LMBs, a message is displayed in the console per LMB
like these ones:
  pseries-hotplug-mem: Memory at 7e0000000 (drc index 8000007e) was hot-added
  pseries-hotplug-mem: Memory at 7f0000000 (drc index 8000007f) was hot-added
  pseries-hotplug-mem: Memory at 800000000 (drc index 80000080) was hot-added
  pseries-hotplug-mem: Memory at 810000000 (drc index 80000081) was hot-added

When adding 1TB of memory and LMB size is 256MB, this leads to 4096
messages to be displayed on the console. These messages are not really
helpful for the end user, so moving them to the DEBUG level.

Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
[mpe: Tweak change log wording]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201211145954.90143-1-ldufour@linux.ibm.com