ARM: dts: msm: Add LCDB BST node for PMI632

The driver requires all the 3 nodes (bst, ldo, ncp) defined
for a proper initialization sequence. Without any of them it
skips the device tree parsing and variables stay un-initialized
causing incorrect configuration.

Change-Id: I452a7a87316b724c9263664eb6be7e941a87a3c5
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>