machine/atsamd21: extracts functionality for processor family into shared files.

Signed-off-by: Ron Evans <ron@hybridgroup.com>

src/machine/board_itsybitsy-m0.go

@@ -1,4 +1,4 @@
-// +build sam,atsamd21g18a,itsybitsy_m0
+// +build sam,atsamd21,itsybitsy_m0
 
 package machine
 

src/machine/machine_atsamd21.go

@@ -1,4 +1,4 @@
-// +build sam,atsamd21g18a
+// +build sam,atsamd21
 
 // Peripheral abstraction layer for the atsamd21.
 //

src/runtime/runtime_atsamd21.go

@@ -1,4 +1,4 @@
-// +build sam,atsamd21g18a
+// +build sam,atsamd21
 
 package runtime
 

targets/atsamd21g18a.json

@@ -1,13 +1,13 @@
 {
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv6m-none-eabi",
-	"build-tags": ["atsamd21g18", "sam"],
+	"build-tags": ["atsamd21g18", "atsamd21", "sam"],
 	"cflags": [
 		"--target=armv6m-none-eabi",
 		"-Qunused-arguments"
 	],
 	"ldflags": [
-		"-T", "targets/atsamd21g18.ld"
+		"-T", "targets/atsamd21.ld"
 	],
 	"extra-files": [
 		"src/device/sam/atsamd21g18a.s"

targets/itsybitsy-m0.json

@@ -1,5 +1,5 @@
 {
-    "inherits": ["atsamd21g18"],
+    "inherits": ["atsamd21g18a"],
     "build-tags": ["sam", "atsamd21g18a", "itsybitsy_m0"],
     "flash": "bossac -d -i -e -w -v -R --offset=0x2000 {hex}"
 }