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>

src/machine/machine_rp2_resets.go

@@ -0,0 +1,31 @@
+//go:build rp2040 || rp2350
+
+package machine
+
+import (
+	"device/rp"
+	"unsafe"
+)
+
+var resets = (*rp.RESETS_Type)(unsafe.Pointer(rp.RESETS))
+
+// resetBlock resets hardware blocks specified
+// by the bit pattern in bits.
+func resetBlock(bits uint32) {
+	resets.RESET.SetBits(bits)
+}
+
+// unresetBlock brings hardware blocks specified by the
+// bit pattern in bits out of reset.
+func unresetBlock(bits uint32) {
+	resets.RESET.ClearBits(bits)
+}
+
+// unresetBlockWait brings specified hardware blocks
+// specified by the bit pattern in bits
+// out of reset and wait for completion.
+func unresetBlockWait(bits uint32) {
+	unresetBlock(bits)
+	for !resets.RESET_DONE.HasBits(bits) {
+	}
+}