Not in the BIOS. Like Gussy said ^^^^ Thats one option. I cloned to another SATAIII SSD then installed the second NVMe drive, wiped the first then once I had the array set up I cloned back to the array.
Regardless you WILL need the latest IRST drivers and software package. You set up the raid in the software.
Winraid has a nice listing of downloads, Thanks Fernando
http://www.win-raid.com/t2f23-Intel-RST-RSTe-Drivers-newest-v-WHQL-v-WHQL.html
“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein