[POWERPC] add support for dumping spu info from xmon

[POWERPC] add support for dumping spu info from xmon

This patch adds a command to xmon for dumping information about
spu structs. The command is 'sf' for "spu fields" perhaps, and
takes the spu number as an argument. This is the same value as the
spu->number field, or the "phys-id" value of a context when it is
bound to a physical spu.

We try to catch memory errors as we dump each field, hopefully this
will make the command reasonably robust, but YMMV. If people see a
need we can easily add more fields to the dump in future.

Output looks something like this:

0:mon> sf 0
Dumping spu fields at address c00000001ffd9e80:
  number                  = 0x0
  name                    = spe
  devnode->full_name      = /cpus/PowerPC,BE@0/spes/spe@0
  nid                     = 0x0
  local_store_phys        = 0x20000000000
  local_store             = 0xd0000800801e0000
  ls_size                 = 0x0
  isrc                    = 0x4
  node                    = 0x0
  flags                   = 0x0
  dar                     = 0x0
  dsisr                   = 0x0
  class_0_pending         = 0
  irqs[0]                 = 0x16
  irqs[1]                 = 0x17
  irqs[2]                 = 0x24
  slb_replace             = 0x0
  pid                     = 0
  prio                    = 0
  mm                      = 0x0000000000000000
  ctx                     = 0x0000000000000000
  rq                      = 0x0000000000000000
  timestamp               = 0x0000000000000000
  problem_phys            = 0x20000040000
  problem                 = 0xd000080080220000
  problem->spu_runcntl_RW = 0x0
  problem->spu_status_R   = 0x0
  problem->spu_npc_RW     = 0x0
  priv1                   = 0xd000080080240000
  priv1->mfc_sr1_RW       = 0x33
  priv2                   = 0xd000080080250000

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>