PCI: pciehp: Replace pciehp_debug module param with dyndbg

PCI: pciehp: Replace pciehp_debug module param with dyndbg

Previously pciehp debug messages were enabled by the pciehp_debug module
parameter, e.g., by booting with this kernel command line option:

  pciehp.pciehp_debug=1

Convert this mechanism to use the generic dynamic debug (dyndbg) feature.
After this commit, pciehp debug messages are enabled by building the kernel
with CONFIG_DYNAMIC_DEBUG=y and booting with this command line option:

  dyndbg="file pciehp* +p"

The dyndbg facility is much more flexible: messages can be enabled at boot-
or run-time based on the file name, function name, line number, message
test, etc.  See Documentation/admin-guide/dynamic-debug-howto.rst for more
details.

Link: https://lore.kernel.org/lkml/20190509141456.223614-7-helgaas@kernel.org
Signed-off-by: Frederick Lawler <fred@fredlawl.com>
[bhelgaas: commit log, comment, remove pciehp_debug parameter]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>