Add XIAO Wio-SX1262 overlay; support SX12xx bandwidths (including 62.5 kHz) as default

- boards/seeed/xiao_wio_sx1262: add overlay, .conf, board.yml
- app: support full set of SX12xx bandwidths; default BW set to 62 (62.5 kHz)
- Update Kconfig and prj.conf
- Update lora_modem.h/c for validation and mapping

build/zephyr/include/generated/app_smem.ld

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/*
+ * This hackish way of including files is due to CMake issues:
+ *   https://gitlab.kitware.com/cmake/cmake/issues/11985
+ *   https://gitlab.kitware.com/cmake/cmake/issues/13718
+ *
+ * When using the "Unix Makefiles" generator, CMake simply
+ * greps for "#include" to generate dependency list.
+ * So if doing it normally, both files are being included
+ * in the dependency list. This creates weird dependency
+ * issue:
+ *
+ *   1. Using A.ld to create a linker script A.cmd.
+ *   2. Using A.cmd to generate A_prebuilt.elf.
+ *   3. Using A_prebuilt.elf to create B.ld.
+ *   4. Creating B.cmd with B.ld.
+ *   5. Creating B_prebuilt.elf using B.cmd.
+ *
+ * Since the dependency list of A.cmd contains both
+ * A.ld and B.ld, when make is invoked again, B.ld
+ * is newer than A.cmd so everything from this point on
+ * gets rebuilt. In order to break this cycle, this
+ * hackish needs to be used since CMake does not parse
+ * macros, and thus these will not appear in
+ * the dependency list. The dependencies should then be
+ * put in CMakeLists.txt instead.
+ *
+ * Note: Ninja generator does not suffer from this issue.
+ */
+#ifdef LINKER_APP_SMEM_UNALIGNED
+#define APP_SMEM_LD <app_smem_unaligned.ld>
+#else
+#define APP_SMEM_LD <app_smem_aligned.ld>
+#endif
+
+#include APP_SMEM_LD
+#undef APP_SMEM_LD