regulator: lcdb: Correct the typo in pull down strength programming

There is a typo in programming the BST_PD_CTL value. Due to
this NCP_PD_STRENGTH register is programmed instead of the
BST_PD_STRENGTH. Fix it.

Change-Id: If630056f77194d3fdfa30b7c1ddd61f74da04cff
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>