arches: centralize noinit linker defintiions

This had been copy-pasted between linker scripts, create
a central header for it.

The linker scripts for xtensa and posix have very different
structure and have been left alone.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/linker/common-noinit.ld

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2020 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+SECTION_PROLOGUE(_NOINIT_SECTION_NAME,(NOLOAD),)
+{
+        /*
+         * This section is used for non-initialized objects that
+         * will not be cleared during the boot process.
+         */
+        *(.noinit)
+        *(".noinit.*")
+
+/* Located in generated directory. This file is populated by the
+ * zephyr_linker_sources() Cmake function.
+ */
+#include <snippets-noinit.ld>
+
+} GROUP_DATA_LINK_IN(RAMABLE_REGION, RAMABLE_REGION)