intel_alpm: Fix wrong offset for PORT_ALPM_* registers

PORT_ALPM_* registers are using MMIO_TRANS2 macro. This is not correct as
they are port register. Use _PORT_MMIO instead.

Fixes: 4ee30a44 ("drm/i915/alpm: Add ALPM register definitions")
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618053026.3268759-10-jouni.hogander@intel.com