machine/hifive1b: fix compiling in simulation (wasm)

src/machine/board_fe310.go

@@ -2,8 +2,6 @@
 
 package machine
 
-import "device/sifive"
-
 const (
 	P00 Pin = 0
 	P01 Pin = 1
@@ -38,10 +36,3 @@ const (
 	P30 Pin = 30
 	P31 Pin = 31
 )
-
-// SPI on the HiFive1.
-var (
-	SPI1 = SPI{
-		Bus: sifive.QSPI1,
-	}
-)

src/machine/board_hifive1b_baremetal.go

@@ -0,0 +1,12 @@
+// +build fe310,hifive1b
+
+package machine
+
+import "device/sifive"
+
+// SPI on the HiFive1.
+var (
+	SPI1 = SPI{
+		Bus: sifive.QSPI1,
+	}
+)