Fix Skylake PEBS data source for perf v5

[Andi Kleen]

Fix data source reporting for Skylake and Skylake Server.
The encodings have changed to express support for L4 and persistent
memory. 

The first patch is a (independent) cleanup.

The second is for the kernel and the third/fourth for perf/tools.
The kernel part and perf tools will compile independently.

Also available in 
git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git perf/skx-data-src-7

v1:
Initial post
v2:
Merged some patches.
Change encoding to use special bit for each combination instead
of modifiers.
v3: 
Switch to new generic lvlnum indication
v4:
Repost. No changes.
v5:
ported to latest tree. Retested remote HITM.