boards: rename qemu_xtensa to qemu_xtensa/dc233c

This is in preparation for adding another SoC where qemu_xtensa
is no longer valid choice. So use qemu_xtensa/dc233c as it is
the same as the old qemu_xtensa.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

tests/lib/heap/testcase.yaml

@@ -3,14 +3,14 @@
 # minutes (vs. ~20 seconds for qemu) to complete in CI.  There's
 # little value there, this is a unit test of library code and we have
 # coverage of the RISC-V architectures via qemu platforms already.
-# Excludes qemu_xtensa due to pathological runtimes which cannot be
+# Excludes qemu_xtensa/dc233c due to pathological runtimes which cannot be
 # reproduced on real hardware.
 tests:
   libraries.heap:
     tags: heap
     platform_exclude:
       - m2gl025_miv
-      - qemu_xtensa
+      - qemu_xtensa/dc233c
       - esp32s2_saola
       - esp32s2_lolin_mini
     timeout: 480

tests/lib/mpsc_pbuf/testcase.yaml

@@ -14,7 +14,8 @@ tests:
       - qemu_riscv64
       - qemu_x86
       - qemu_x86_64
-      - qemu_xtensa
+      - qemu_xtensa/dc233c
+      - native_posix
       - native_sim
     integration_platforms:
       - native_sim