Add RP2350 support (#4459)

machine/rp2350: add support

* add linker scripts for rp2350
* add bootloader
* begin melding rp2040 and rp2350 APIs
* add UART
* add rp2350 boot patching
* Fix RP2350 memory layout (#4626)
* Remove rp2040-style second stage bootloader.
* Add 'minimum viable' IMAGE_DEF embedded block
* Create a pico2 specific target
* Implement rp2350 init, clock, and uart support
* Merge rp2 reset code back together
* Separate chip-specific clock definitions
* Clear pad isolation bit on rp2350
* Init UART in rp2350 runtime
* Correct usb/serial initialization order
* Implement jump-to-bootloader
* test: add pico2 to smoketests

---------

Signed-off-by: deadprogram <ron@hybridgroup.com>
Co-authored-by: Matthew Mets <matt.mets@cibomahto.com>
Co-authored-by: Matt Mets <matt@blinkinlabs.com>
Co-authored-by: deadprogram <ron@hybridgroup.com>

tools/gen-device-svd/gen-device-svd.go

@@ -909,8 +909,9 @@ func writeGo(outdir string, device *Device, interruptSystem string) error {
 
 //go:build {{.pkgName}} && {{.device.Metadata.NameLower}}
 
+/*
 {{.device.Metadata.Description}}
-//
+*/
 {{.device.Metadata.LicenseBlock}}
 package {{.pkgName}}
 
@@ -1357,8 +1358,10 @@ func writeAsm(outdir string, device *Device) error {
 	t := template.Must(template.New("go").Parse(`// Automatically generated file. DO NOT EDIT.
 // Generated by gen-device-svd.go from {{.File}}, see {{.DescriptorSource}}
 
+/*
 {{.Description}}
-//
+*/
+
 {{.LicenseBlock}}
 
 .syntax unified