ARM: dts: msm: support PM855L BOB dynamic mode configuration on SDM855

Add support to allow consumers to dynamically control the mode of
PM855L BOB at runtime.  Implement the following mapping for
pm855l_bob load current requests:

Current (uA)    Active Mode    Sleep Mode
 >= 2000000        PWM            PWM
 >= 1000000        AUTO           PFM
  < 1000000        AUTO           PASS

Change-Id: I789ddf728238765a49e6780b55c6613296a59a98
Signed-off-by: David Collins <collinsd@codeaurora.org>