PCI: trace: Add PCI controller tracepoint feature

PCI: trace: Add PCI controller tracepoint feature

Some PCI controllers may provide debug functionalities to track PCI bus
activities like LTSSM state transitions and data rate changes. These will
be very useful for debugging PCI link specific issues such as endpoint not
getting detected or performance issues.

Hence, implement the PCI controller tracepoint feature for recording LTSSM
state transitions and data rate changes.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
[mani: commit log and maintainers entry]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://patch.msgid.link/1774403912-210670-2-git-send-email-shawn.lin@rock-chips.com