This reverts commit 645d6945.

The commit cause issues with memory access from the device side.
Switch back to write-combined memory mappings until the issues
will be properly addressed.

Add extra wmb() needed when boot_params->save_restore_ret_address() is
modified.
Reviewed-by: Karol Wachowski <karol.wachowski@linux.intel.com>
Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231017121353.532466-1-stanislaw.gruszka@linux.intel.com