drm/i915/psr: Configure PIPE_SRCSZ_ERLY_TPT for psr2 early transport

There is a new register used to configure selective update area size
for early transport.

Configure PIPE_SRCSZ_ERLY_TPT using calculated selective update area
carried in crtc_state->su_area.

Bspec: 68927

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231218175004.52875-6-jouni.hogander@intel.com