drm/amd/display: make firmware info only load once during dc_bios create

Currently every time DC wants to access firmware info we make a call
into VBIOS. This makes no sense as there is nothing that can change
runtime inside fw info and can cause issues when calling unstable
bios during bringup.

This change eliminate this behavior by only calling bios once for fw
info and keeping it stored as part of dc_bios.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Chris Park <Chris.Park@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>