drm/msm/dp: do not validate streams for HDR

User-space can set HDR metadata before setting up stream.
As driver can cache the metadata, do not validate streams
on HDR setup to avoid unnecessary failures during HDR
setup.

CRs-Fixed: 2267392
Change-Id: Ib984be3a9db1be735f978f7e184fa87fc967f31a
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>