arch_topology: Update cpu core sibling mask at topology initialization

Commit 'f4218db1948b100c("sched: Introduce the concept CPU clusters in
the scheduler")' added initializing cpu core sibling mask at cpu
topology initialization to get all possible cpus in cluster, which is
used for WALT initializations. This part missed while porting for msm-4.14
kernel. When system booted with boot_cpus option,it boots only cpus in
boot_cpus, then all possible cpus would not be part of core sibling mask.
Which causes wrong initialization at WALT.

Add the core sibling mask updation at cpu topology initialization to avoid
abnormal WALT initializations.

Change-Id: I0567672ad5fb67d211d9336181ceb53b9f6023af
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>