cxl: Name interrupts in /proc/interrupt

Currently all interrupts generated by cxl are named "cxl".  This is not very
informative as we can't distinguish between cards, AFUs, error interrupts, user
contexts and user interrupts numbers.  Being able to distinguish them is useful
for setting affinity.

This patch gives each of these names in /proc/interrupts.

A two card CAPI system, with afu0.0 having 2 active contexts each with 4 user
IRQs each, will now look like this:

    % grep cxl /proc/interrupts
    444:          0  OPAL ICS 141312 Level     cxl-card1-err
    445:          0  OPAL ICS 141313 Level     cxl-afu1.0-err
    446:          0  OPAL ICS 141314 Level     cxl-afu1.0
    462:          0  OPAL ICS 2052 Level     cxl-afu0.0-pe0-1
    463:      75517  OPAL ICS 2053 Level     cxl-afu0.0-pe0-2
    468:          0  OPAL ICS 2054 Level     cxl-afu0.0-pe0-3
    469:          0  OPAL ICS 2055 Level     cxl-afu0.0-pe0-4
    470:          0  OPAL ICS 2056 Level     cxl-afu0.0-pe1-1
    471:      75506  OPAL ICS 2057 Level     cxl-afu0.0-pe1-2
    472:          0  OPAL ICS 2058 Level     cxl-afu0.0-pe1-3
    473:          0  OPAL ICS 2059 Level     cxl-afu0.0-pe1-4
    502:       1066  OPAL ICS 2050 Level     cxl-afu0.0
    514:          0  OPAL ICS 2048 Level     cxl-card0-err
    515:          0  OPAL ICS 2049 Level     cxl-afu0.0-err

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>