drm/i915/display: Make intel_dp_aux_fw_sync_len available for PSR code

drm/i915/display: Make intel_dp_aux_fw_sync_len available for PSR code

ALPM AUX-Wake fast wake sync pulse count is needed by PSR to calculate IO
wake and fast wake lines. Convert intel_dp_aux_fw_sync_len as non-static
to make it available for PSR code.

v2: use int instead of u8

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240313133221.868391-2-jouni.hogander@intel.com