board: sifive: unmatched: enable booting on a second NVME device

The HiFive Unmatched board has a M2 slot for NVME and a PCIe slot that
can also be used for NVME. Enable support for a second NVME device, so
that software RAID-1 configurations can be supported at the u-boot
level.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/configs/sifive-unmatched.h b/include/configs/sifive-unmatched.h
index 24904aa..74150b7 100644
--- a/include/configs/sifive-unmatched.h
+++ b/include/configs/sifive-unmatched.h
@@ -17,6 +17,7 @@
 
 #define BOOT_TARGET_DEVICES(func) \
 	func(NVME, nvme, 0) \
+	func(NVME, nvme, 1) \
 	func(USB, usb, 0) \
 	func(MMC, mmc, 0) \
 	func(SCSI, scsi, 0) \