msm: sde: avoid re-configuration during inline validate

Inline validation is currently using session config to
validate configuration. This will modify configuration
while inline commit is in progress. Avoid modifying
session configuration during inline validate by calling
new session validation function that does not modify
session state.

Change-Id: Iee38672439bdee291d1fc832d561c26723becbc3
Signed-off-by: Alan Kwong <akwong@codeaurora.org>