defconfig: sdm845: enable regulator proxy consumer driver

Enable the proxy consumer driver so that regulators may be kept
at a certain minimum level during boot.  This allows all
consumers to make their requests without interfering with each
other.

Change-Id: I7169e6f8f23a41e95548a51781650d37521570ed
Signed-off-by: David Collins <collinsd@codeaurora.org>