serial: set baud rate to 921600

921600 (8×115200) is a more standard baud rate than 1000000
apparently.

fpga/serial.sv

@@ -37,7 +37,7 @@ module serial (
    // The term "divisor" here is probably misleading, since it is
    // actually a fixed-point *multiplier* which is <= 1.
    //
-   parameter [31:0]	BAUDRATE = 1000000;
+   parameter [31:0]	BAUDRATE = 921600;
    parameter [31:0]	TTY_CLK  = 84000000;
    parameter		NCO_BITS = 24;
    parameter            BREAK_BITS = 19; // 2^19/(BAUDRATE*16) ~ 33 ms