dt-bindings: esoc: Add spmi soft reset property

Add esoc-spmi-soft-reset property which if set in the dt-node indicates
that qpnp apis will be used to reset the external modem chip.

Change-Id: I117128b7c322ec8f4da73e45506daa191f8cc3e3
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>