drm/i915/display/adl_p: Disable PSR2

We are missing the implementation of some workarounds to enabled PSR2
in Alderlake P, so to avoid any CI report of issues around PSR2
disabling it until all PSR2 workarounds are implemented.

Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210524214805.259692-5-jose.souza@intel.com