powerpc/smp: Parse ibm,thread-groups with multiple properties

The "ibm,thread-groups" device-tree property is an array that is used
to indicate if groups of threads within a core share certain
properties. It provides details of which property is being shared by
which groups of threads. This array can encode information about
multiple properties being shared by different thread-groups within the
core.

Example: Suppose,
"ibm,thread-groups" = [1,2,4,8,10,12,14,9,11,13,15,2,2,4,8,10,12,14,9,11,13,15]

This can be decomposed up into two consecutive arrays:

a) [1,2,4,8,10,12,14,9,11,13,15]
b) [2,2,4,8,10,12,14,9,11,13,15]

where in,

a) provides information of Property "1" being shared by "2" groups,
   each with "4" threads each. The "ibm,ppc-interrupt-server#s" of the
   first group is {8,10,12,14} and the "ibm,ppc-interrupt-server#s" of
   the second group is {9,11,13,15}. Property "1" is indicative of
   the thread in the group sharing L1 cache, translation cache and
   Instruction Data flow.

b) provides information of Property "2" being shared by "2" groups,
   each group with "4" threads. The "ibm,ppc-interrupt-server#s" of
   the first group is {8,10,12,14} and the
   "ibm,ppc-interrupt-server#s" of the second group is
   {9,11,13,15}. Property "2" indicates that the threads in each group
   share the L2-cache.

The existing code assumes that the "ibm,thread-groups" encodes
information about only one property. Hence even on platforms which
encode information about multiple properties being shared by the
corresponding groups of threads, the current code will only pick the
first one. (In the above example, it will only consider
[1,2,4,8,10,12,14,9,11,13,15] but not [2,2,4,8,10,12,14,9,11,13,15]).

This patch extends the parsing support on platforms which encode
information about multiple properties being shared by the
corresponding groups of threads.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1607596739-32439-2-git-send-email-ego@linux.vnet.ibm.com

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