regulator: core: Add option to suppress regulator info messages

Each call to regulator_register() results in a line being written
into the kmsg log.  regulator_init_complete() also prints a line for
each unused regulator which is automatically disabled.

Add a function named regulator_suppress_info_printing() which can
be called to disable these print statements.

Change-Id: Ic4c723b7d02a494b4e261858d699d9625da715ea
Signed-off-by: David Collins <collinsd@codeaurora.org>