machine: bump rp2040 to 200MHz (#4768)

* machine: add support for core voltage adjustments to rp2040

In preparation for bumping the core frequency of the rp2040, this
change implements the required core voltage adjustment logic.

* machine: bump rp2040 to 200MHz

src/machine/machine_rp2_clocks.go

@@ -42,6 +42,10 @@ type clock struct {
 	cix clockIndex
 }
 
+// The delay in seconds for core voltage adjustments to
+// settle. Taken from the Pico SDK.
+const _VREG_VOLTAGE_AUTO_ADJUST_DELAY = 1 / 1e3
+
 // clock returns the clock identified by cix.
 func (clks *clocksType) clock(cix clockIndex) clock {
 	return clock{
@@ -188,6 +192,14 @@ func (clks *clocksType) init() {
 		xoscFreq,
 		xoscFreq)
 
+	if adjustCoreVoltage() {
+		// Wait for the voltage to settle.
+		const cycles = _VREG_VOLTAGE_AUTO_ADJUST_DELAY * xoscFreq * MHz
+		for i := 0; i < cycles; i++ {
+			arm.Asm("nop")
+		}
+	}
+
 	// clkSys = pllSys (125MHz) / 1 = 125MHz
 	csys := clks.clock(clkSys)
 	csys.configure(rp.CLOCKS_CLK_SYS_CTRL_SRC_CLKSRC_CLK_SYS_AUX,