rp2xxx: Add support for assembling RP2350-specific PIO

[Grazfather]

RP2350 adds the following new instruction features:

• Adds PINCTRL_JMP_PIN as a source for the WAIT instruction, plus an offset in the range 0-3.
  • This gives WAIT pin arguments a per-SM mapping that is independent of the IN-mapped pins.
• Adds PINDIRS as a destination for MOV.
  • This allows changing the direction of all OUT-mapped pins with a single instruction: MOV PINDIRS, NULL or MOV
    PINDIRS, ~NULL
• [ ] Adds SM IRQ flags as a source for MOV x, STATUS
  • This allows branching (as well as blocking) on the assertion of SM IRQ flags.
• Extends IRQ instruction encoding to allow state machines to set, clear and observe IRQ flags from different PIO
  blocks.
  • There is no delay penalty for cross-PIO IRQ flags: an IRQ on one state machine is observable to all state
    machines on the next cycle.
• Adds the FJOIN_RX_GET FIFO mode.
  • A new MOV encoding reads any of the four RX FIFO storage registers into OSR.
  • This instruction permits random reads of the four FIFO entries, indexed either by instruction bits or the Y
    scratch register.
• Adds the FJOIN_RX_PUT FIFO mode.
  • A new MOV encoding writes the ISR into any of the four RX FIFO storage registers.
  • The registers are indexed either by instruction bits or the Y scratch register.
    RP2350 adds the following security features:
• Limits Non-secure PIOs (set to via ACCESSCTRL) to observation of only Non-secure GPIOs. Attempting to read a
  Secure GPIO returns a 0.
• Disables cross-PIO functionality (IRQs, CTRL_NEXTPREV operations) between Non-secure PIO blocks (those which
  permit Non-secure access according to ACCESSCTRL) and Secure-only blocks (those which do not).
  RP2350 includes the following general improvements:
• Increased the number of PIO blocks from two to three (8 → 12 state machines).
• Improved GPIO input/output delay and skew.
• Reduced DMA request (DREQ) latency by one cycle vs RP2040

[mattnite]

@Grazfather there's one item unchecked, I take it you forgot to check it?

[Grazfather]

@mattnite I don't understand that one. I don't see any difference in the encoding of the (plain) mov instruction in https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf (page 893).