drivers: serial: Add support for group interrupt in the serial driver

Apply the grp irq support in serial driver for MCB-RX26T

Signed-off-by: Quy Tran <[email protected]>

Author: quytranpzz

boards/renesas/mcb_rx26t/mcb_rx26t_defconfig

@@ -6,7 +6,7 @@ CONFIG_GPIO=y
 
 # Enable UART driver
 CONFIG_SERIAL=y
-CONFIG_UART_INTERRUPT_DRIVEN=n
+CONFIG_UART_INTERRUPT_DRIVEN=y
 
 # Enable console
 CONFIG_CONSOLE=y