tests: Fix the platform exclude board name

qemu_xtensa_dc233c didn't pan out like I expected, needed to be
qemu_xtensa/dc233c/mmu to be excluded.

Signed-off-by: Tom Burdick <[email protected]>

Author: teburd

tests/subsys/rtio/rtio_api/testcase.yaml

@@ -1,7 +1,7 @@
 common:
   # renode causes timeouts unfortunately
   # xtensa dc233 (with mmu) has a TLB exception for unclear reasons
-  platform_exclude: m2gl025_miv m5stack_core2 hifive1 qemu_xtensa_dc233c
+  platform_exclude: m2gl025_miv m5stack_core2 hifive1 qemu_xtensa/dc233c/mmu
   platform_key:
     - arch
     - simulation