usb: pd: Add support to disable pps capability

This change introduces a DT property through which pps
capability can be disabled. Standard PD communication will
remain unaffected.

Change-Id: Ib65fb460a4158034e7d371ad7b83f0a17418cf9d
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>