Perf cannot parse UPI (Intel's "Ultra Path Interconnect" [1]) events.

    # perf stat -e UPI_DATA_BANDWIDTH_TX
    event syntax error: 'UPI_DATA_BANDWIDTH_TX'
                     \___ parser error
    Run 'perf list' for a list of valid events

The JSON lists call the box UPI LL, while perf calls it upi.  Add
conversion support to JSON to convert the unit properly.

Committer notes:

[1] https://en.wikipedia.org/wiki/Intel_Ultra_Path_Interconnect

"The Intel Ultra Path Interconnect (UPI) is a point-to-point processor
interconnect developed by Intel which replaced the Intel QuickPath
Interconnect (QPI) in Xeon Skylake-SP platforms starting in 2017.

UPI is a low-latency coherent interconnect for scalable multiprocessor
systems with a shared address space. It uses a directory-based home
snoop coherency protocol with a transfer speed of up to 10.4 GT/s.
Supporting processors typically have two or three UPI links."
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/1557234991-130456-1-git-send-email-kan.liang@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>