PCI/ASPM: Handle PCI-to-PCIe bridges as roots of PCIe hierarchies

In a struct pcie_link_state, link->root points to the pcie_link_state of
the root of the PCIe hierarchy.  For the topmost link, this points to
itself (link->root = link).  For others, we copy the pointer from the
parent (link->root = link->parent->root).

Previously we recognized that Root Ports originated PCIe hierarchies, but
we treated PCI/PCI-X to PCIe Bridges as being in the middle of the
hierarchy, and when we tried to copy the pointer from link->parent->root,
there was no parent, and we dereferenced a NULL pointer:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
  IP: [<ffffffff9e424350>] pcie_aspm_init_link_state+0x170/0x820

Recognize that PCI/PCI-X to PCIe Bridges originate PCIe hierarchies just
like Root Ports do, so link->root for these devices should also point to
itself.

Fixes: 51ebfc92b72b ("PCI: Enumerate switches below PCI-to-PCIe bridges")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=193411
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1022181
Tested-by: lists@ssl-mail.com
Tested-by: Jayachandran C. <jnair@caviumnetworks.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.2+

path: root/sound/soc/txx9/Kconfig

##
## TXx9 ACLC
##
config SND_SOC_TXX9ACLC
	tristate "SoC Audio for TXx9"
	depends on HAS_TXX9_ACLC && TXX9_DMAC
	help
	  This option enables support for the AC Link Controllers in TXx9 SoC.

config HAS_TXX9_ACLC
	bool

config SND_SOC_TXX9ACLC_AC97
	tristate
	select AC97_BUS
	select SND_AC97_CODEC
	select SND_SOC_AC97_BUS


##
## Boards
##
config SND_SOC_TXX9ACLC_GENERIC
	tristate "Generic TXx9 ACLC sound machine"
	depends on SND_SOC_TXX9ACLC
	select SND_SOC_TXX9ACLC_AC97
	select SND_SOC_AC97_CODEC
	help
	  This is a generic AC97 sound machine for use in TXx9 based systems.