tests: posix: xsi_realtime: add integration platforms to testsuite

Use qemu_x86, qemu_cortex_a53, and qemu_riscv64 as integration
test platforms for this testsuite, since both qemu_x86 and
qemu_cortex_a53 both have an MMU available, and qemu_riscv64
can execute quickly that mmu-less systems can also use a subset
of the option group (minus `mmap()`).

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

tests/posix/xsi_realtime/testcase.yaml

@@ -9,6 +9,10 @@ common:
     - simulation
   min_flash: 64
   min_ram: 96
+  integration_platforms:
+    - qemu_x86
+    - qemu_cortex_a53
+    - qemu_riscv64
   platform_exclude:
     # linker_zephyr_pre0.cmd:140: syntax error (??)
     - qemu_xtensa/dc233c