To update SP firmware from the host, use the fwupdate utility, included in Oracle Solaris 11.3 as part of the Oracle Hardware Management Pack (OHMP).
For more information on using the fwpudate utility, refer to "Using fwupdate to Update Firmware" in the Oracle Server CLI Tools for Oracle Solaris 11.3 User Guide
# fwupdate update sysfw-firmware -n sp -f firmware-package-file.pkg
where firmware-package-file.pkg is the path to the firmware package for your server's SP.