[SCSI] libsas: unify domain_device sas_rphy lifetimes

Since the domain_device can out live the scsi_target we need the rphy to
follow suit otherwise we run into issues like:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
  IP: [<ffffffffa011561b>] sas_ata_printk+0x43/0x6f [libsas]
  PGD 0
  Oops: 0000 [#1] SMP
  CPU 1
  Modules linked in: ses enclosure isci libsas scsi_transport_sas fuse sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf microcode pcspkr igb joydev iTCO_wdt ioatdma iTCO_vendor_support i2c_i801 i2c_core dca wmi hed ipv6 pata_acpi ata_generic [last unloaded: scsi_wait_scan]

  Pid: 129, comm: kworker/u:3 Not tainted 3.3.0-rc5-isci+ #1 Intel Corporation SandyBridge Platform/To be filled by O.E.M.
  RIP: 0010:[<ffffffffa011561b>] [<ffffffffa011561b>] sas_ata_printk+0x43/0x6f [libsas]
  RSP: 0018:ffff88042232dd70 EFLAGS: 00010282
  RAX: 0000000000000000 RBX: ffff8804283165b8 RCX: ffff88042232dda0
  RDX: ffff88042232dd78 RSI: ffff8804283165b8 RDI: ffffffffa01188d7
  RBP: ffff88042232ddd0 R08: ffff880388454000 R09: ffff8803edfde1f8
  R10: ffff8803edfde1f8 R11: ffff8803edfde1f8 R12: ffff880428316750
  R13: ffff880388454000 R14: ffff8803f88b31d0 R15: ffff8803f8b21d50
  FS: 0000000000000000(0000) GS:ffff88042ee20000(0000) knlGS:0000000000000000
  CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 0000000000000050 CR3: 0000000001a05000 CR4: 00000000000406e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Process kworker/u:3 (pid: 129, threadinfo ffff88042232c000, task ffff88042230c920)
  Stack:
  0000000000000000 ffff880400000018 ffff88042232dde0 ffff88042232dda0
  ffffffffa01188c4 ffff88042ee93af0 ffff88042232ddb0 ffffffff8100e047
  ffff88042232de10 ffff880420e5a2c8 ffff8803f8b21d50 ffff8803edfde1f8
  Call Trace:
  [<ffffffff8100e047>] ? load_TLS+0xb/0xf
  [<ffffffffa01156ad>] async_sas_ata_eh+0x66/0x95 [libsas]
  [<ffffffff810655e1>] async_run_entry_fn+0x9e/0x131

Reported-by: Tom Jackson <thomas.p.jackson@intel.com>
Tested-by: Tom Jackson <thomas.p.jackson@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>