samd/boards: Add support for the Adafruit QT Py board.

Supporting a variant with an optional SPIFLASH device as well.  Tested both
variants with a QT Py board.

Signed-off-by: robert-hh <robert@hammelrath.com>

ports/samd/boards/ADAFRUIT_QTPY_SAMD21/board.json

@@ -0,0 +1,20 @@
+{
+    "deploy": [
+        "../deploy.md"
+    ],
+    "docs": "",
+    "features": [
+        "USB-C"
+    ],
+    "images": [
+        "qt_py_samd21.jpg"
+    ],
+    "mcu": "samd21",
+    "product": "QT Py - SAMD21",
+    "thumbnail": "",
+    "url": "https://www.adafruit.com/product/4600",
+    "variants": {
+        "SPIFLASH": "Support for an external Flash chip"
+    },
+    "vendor": "Adafruit"
+}

ports/samd/boards/ADAFRUIT_QTPY_SAMD21/mpconfigboard.h

@@ -0,0 +1,6 @@
+#define MICROPY_HW_BOARD_NAME "QT Py"
+#define MICROPY_HW_MCU_NAME   "SAMD21E18A"
+
+#define MICROPY_HW_DFLL_USB_SYNC    (1)
+
+#define MICROPY_HW_SPIFLASH_ID (3)

ports/samd/boards/ADAFRUIT_QTPY_SAMD21/mpconfigboard.mk

@@ -0,0 +1,4 @@
+MCU_SERIES = SAMD21
+CMSIS_MCU = SAMD21E18A
+LD_FILES = boards/samd21x18a.ld sections.ld
+TEXT0 = 0x2000

ports/samd/boards/ADAFRUIT_QTPY_SAMD21/mpconfigvariant_SPIFLASH.mk

@@ -0,0 +1,2 @@
+CFLAGS += -DMICROPY_HW_SPIFLASH=1
+MICROPY_HW_CODESIZE ?= 232K

ports/samd/boards/ADAFRUIT_QTPY_SAMD21/pins.csv

@@ -0,0 +1,25 @@
+A0,PA02
+A1,PA03
+A2,PA04
+A3,PA05
+SDA,PA16
+SCL,PA17
+TX,PA06
+RX,PA07
+SCK,PA11
+MISO,PA09
+MOSI,PA10
+
+NEO_PWR,PA15
+NEOPIX,PA18
+
+FLASH_MOSI,PA22
+FLASH_MISO,PA19
+FLASH_SCK,PA23
+FLASH_CS,PA08
+
+USB_DM,PA24
+USB_DP,PA25
+
+SWCLK,PA30
+SWDIO,PA31