webui: Tie Hardware Update button visibility to usage of BIOS/RAID

If the BIOS and RAID options are not available, then the Hardware Update
button is not needed, so we don't display it. In BIOS or/and RAID
options are available, then we display this button like before.
Merge pull request #550 from vuntz/hardware-update-visibility

webui: Tie Hardware Update button visibility to usage of BIOS/RAID