drivers: serial: add circular mode in uart driver

the following implementations are added:
- set cyclic variable to handle circular/normal mode :
  enable dest/source_reload_en variable to set CIRC bit to 1 for RX or TX.
- DMA_STATUS_COMPLETE(0), DMA_STATUS_BLOCK(1) macros to handle half
 and full irq
- add ASYNC_UART_STATUS_TIMEOUT(3)  macro to work with  default mode
- add status input in uart_stm32_dma_rx_flush function  to handle
 async events depending on the  mode we are in.

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>
co-authored-by: Cyril Fougeray <cyril.fougeray@worldcoin.org>