tests: can.frame: enable can test on qemu_leon3

Enable CAN frame test which does not require a driver implementation
or a network.

Signed-off-by: Martin Åberg <[email protected]>

Author: tbr-tt

tests/subsys/canbus/frame/testcase.yaml

@@ -1,5 +1,5 @@
 common:
-  platform_allow: native_posix native_posix_64 qemu_x86 qemu_cortex_m3
+  platform_allow: native_posix native_posix_64 qemu_x86 qemu_cortex_m3 qemu_leon3
 tests:
   can.frame:
     tags: net