Add support for MKR 1310 onboard flash

The MKR 1310 has an onboard SPI flash identical to what's on the MKRMEM shield.  It currently requires you to pull the LoRa radio into reset, but it's there and usable. It's on SPI1 and the CS pin is on 32 (instead of 5).  I can't figure out how to force it to use SPI1 so that it sees the chip.