Add SPIv1, use cfg_attr to pick correct impl.

Add IRQ to impl_rng!() to accomodate RNG vs HASH_RNG split.

embassy-stm32/src/spi/mod.rs

@@ -0,0 +1,34 @@
+#![macro_use]
+
+#[cfg_attr(feature = "_spi_v1", path = "spi_v1.rs")]
+#[cfg_attr(feature = "_spi_v2", path = "spi_v2.rs")]
+mod spi;
+
+pub use spi::*;
+
+// TODO move upwards in the tree
+pub enum ByteOrder {
+    LsbFirst,
+    MsbFirst,
+}
+
+#[derive(Copy, Clone, PartialOrd, PartialEq)]
+enum WordSize {
+    EightBit,
+    SixteenBit,
+}
+
+#[non_exhaustive]
+pub struct Config {
+    pub mode: Mode,
+    pub byte_order: ByteOrder,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            mode: MODE_0,
+            byte_order: ByteOrder::MsbFirst,
+        }
+    }
+}