drm/amd/display: update psp interface header

[Why]
We need to support SRM(System Renewability Message)
As per hdcp spec (5.Renewability) SRM needs to be storage in a non-volatile
memory.

PSP owns the checking of SRM but doesn't have the ability to store it in a
non-volatile memory. So we need the kernel driver to facilitate it using the
interface provided by PSP

[How]
Add the interface to the header file, so the driver can use them

v2: update commit description

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>