ARM: dts: msm: Define bcl peripheral devicetree node for pmi8937

Currently bcl peripheral node is defined directly under spmi bus node.
But bcl peripheral hardware is part of slave device number 2 in
pmi8937. Define bcl peripheral devicetree node under slave device
number 2 in pmi8937.

Change-Id: I6fcbdf257030aa81c548a523c36de595a1d85f55
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>