Allow partially dynamic profile in the audio policy config

The audio policy configuration deserializer supports fully dynamic
profiles by not setting a profile in a port.
It also supports partially dynamic profile by
not setting @format, @samplingRates or @channelMasks

Nevertheless this last feature of partial dynamic profile
was mistakenly not allowed by the configuration xsd.

Bug: 63541622
Change-Id: I78f77a77a3c62bba28a7da5a0e3c8c608b5a01d9
Signed-off-by: Kevin Rocard <krocard@google.com>