Currently PSR2 SU Region Early Transport is enabled by default on Lunarlake
if panel supports it despite enable_psr module parameter value. This patch
makes it possible for user to limit used PSR mode and prevent SU Region
Early Transport by setting enable_psr as 2. With default (-1) PSR2 SU
Region Early Transport is allowed.

v2: fix/improve commit desciption
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618053026.3268759-6-jouni.hogander@intel.com