embassy-stm32/eth: consolidate v1a/v1c and add v1b

The only differences between v1a and v1c were clocks and GPIO, v1b will
likely work out of the box (or simply need minor tweaks)

embassy-stm32/src/eth/mod.rs

@@ -1,9 +1,7 @@
 #![macro_use]
 
-#[cfg_attr(eth_v1a, path = "v1a/mod.rs")]
-#[cfg_attr(eth_v1c, path = "v1c/mod.rs")]
+#[cfg_attr(any(eth_v1a, eth_v1b, eth_v1c), path = "v1/mod.rs")]
 #[cfg_attr(eth_v2, path = "v2/mod.rs")]
-#[cfg_attr(eth_v1, path = "v1.rs")]
 mod _version;
 pub mod generic_smi;