Refactor LPUART driver constructors (#51)

* Refactor LPUART driver constructors

- Add new_with_rtscts(), new_with_rts(), new_with_cts() methods
- Store RTS/CTS pins in TX/RX structs
- Remove enable_tx, enable_rx, enable_rx_rts, enable_tx_cts config fields
- Fix typo: msb_firs -> msb_first
- Fix write_byte() return type to Result<()>

* Update hello example for LPUART driver changes

* Refactor buffered LPUART initialization logic

- Split new_inner() into init_common() and separate helpers for full-duplex, TX-only, and RX-only
- Replace assert!() with proper Error::InvalidArgument returns for empty buffers
- Simplify constructor implementations by removing expect() calls

1 files changed, 0 insertions, 2 deletions

diff --git a/examples/src/bin/lpuart_polling.rs b/examples/src/bin/lpuart_polling.rs
index 9cea418cc..b80668834 100644
--- a/examples/src/bin/lpuart_polling.rs
+++ b/examples/src/bin/lpuart_polling.rs
@@ -19,8 +19,6 @@ async fn main(_spawner: Spawner) {
     // Create UART configuration
     let config = Config {
         baudrate_bps: 115_200,
-        enable_tx: true,
-        enable_rx: true,
         ..Default::default()
     };