Firmware: Runtime WRPLL

runtime: drive CLK_SEL to true when si549 is used
runtime & libboard_artiq: allow standalone to use io_expander
si549: add bit bang mmcm dynamic configuration
si549: add frequency counter for refclk
rtio_clocking & si549: add 125Mhz wrpll refclk setup

src/runtime/src/rtio_clocking.rs

@@ -357,9 +357,6 @@ fn get_si549_setting(clk: RtioClock) -> si549::FrequencySetting {
         RtioClock::Ext0_Synth0_125to125 => {
             info!("using 125MHz reference to make 125MHz RTIO clock with WRPLL");
         }
-        RtioClock::Int_150 => {
-            info!("using internal 150MHz RTIO clock");
-        }
         RtioClock::Int_100 => {
             info!("using internal 100MHz RTIO clock");
         }