atsame5x: add support for CAN

targets/atsame54-xpro.json

@@ -2,5 +2,6 @@
     "inherits": ["atsame54p20a"],
     "build-tags": ["atsame54_xpro"],
     "flash-method": "openocd",
-    "openocd-interface": "cmsis-dap"
+    "openocd-interface": "cmsis-dap",
+    "default-stack-size": 4096
 }

targets/atsame54p20a.json

@@ -1,6 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
-	"build-tags": ["sam", "atsame5x", "atsame54p20", "atsame54p20a"],
+	"build-tags": ["sam", "atsame5x", "atsame54", "atsame54p20", "atsame54p20a"],
 	"linkerscript": "targets/atsame5xx20-no-bootloader.ld",
 	"extra-files": [
 		"src/device/sam/atsame54p20a.s"

targets/feather-m4-can.json

@@ -4,5 +4,6 @@
     "flash-1200-bps-reset": "true",
     "flash-method": "msd",
     "msd-volume-name": "FTHRCANBOOT",
-    "msd-firmware-name": "firmware.uf2"
+    "msd-firmware-name": "firmware.uf2",
+    "default-stack-size": 4096
 }