Various updates to the PCI-express capability output.

• Group the output so that it follows the capability register set more closely. The first line now contains device information and the second line contains link information. As a result, ARI status is now output on the first line, and the link width is moved down to the second line of link information.
• Only read the DEVICE_CAP2 register to check for ARI if the capability version is >= 2.
• Don't output any link information if the link capability and status registers are zero.
• Label the MSI interrupt index value as "MSI" instead of "IRQ".