kselftest/arm64: Fix check_tags_inclusion test

The check_tags_inclusion test reports the error below because the test
plan is not declared correctly:

  # Planned tests != run tests (0 != 4)

Fix the test adding the correct test plan declaration.

Fixes: f3b2a26c ("kselftest/arm64: Verify mte tag inclusion via prctl")
Cc: Shuah Khan <shuah@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Gabor Kertesz <gabor.kertesz@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

tools/testing/selftests/arm64/mte/check_tags_inclusion.c

@@ -170,6 +170,9 @@ int main(int argc, char *argv[])
 	/* Register SIGSEGV handler */
 	mte_register_signal(SIGSEGV, mte_default_handler);
 
+	/* Set test plan */
+	ksft_set_plan(4);
+
 	evaluate_test(check_single_included_tags(USE_MMAP, MTE_SYNC_ERR),
 		      "Check an included tag value with sync mode\n");
 	evaluate_test(check_multiple_included_tags(USE_MMAP, MTE_SYNC_ERR),