added UART interrupts driver for Raspberry Pi Pico board
moved baudrate from config to data structure
Signed-off-by: Andrei-Edward Popa <andrei_edward.popa@upb.ro>
if peripheral clock is not configured, uart init API function returns 0,
so we need to check the return value of this function
Signed-off-by: Andrei-Edward Popa <andrei_edward.popa@upb.ro>