drm/i915/psr: Calculate PIPE_SRCSZ_ERLY_TPT value

When early transport is enabled we need to write PIPE_SRCSZ_ERLY_TPT on
every flip doing selective update. This patch calculates
PIPE_SRCSZ_ERLY_TPT same way as is done for PSR2_MAN_TRK_CTL value and
stores i in intel_crtc_state->pipe_srcsz_early_tpt to be written later
during flip.

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/20240319123327.1661097-2-jouni.hogander@intel.com