tests: cleanup cbprintf tag usage

Add cbprintf tag were missing and change prf to cbprintf to be
consistent.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
diff --git a/tests/lib/cbprintf_fp/testcase.yaml b/tests/lib/cbprintf_fp/testcase.yaml
index 9b99355..f4a4d48 100644
--- a/tests/lib/cbprintf_fp/testcase.yaml
+++ b/tests/lib/cbprintf_fp/testcase.yaml
@@ -1,6 +1,7 @@
 common:
   harness: console
   platform_exclude: native_posix native_posix_64 nrf52_bsim
+  tags: cbprintf
   integration_platforms:
     - qemu_x86
     - qemu_x86_64
diff --git a/tests/unit/cbprintf/testcase.yaml b/tests/unit/cbprintf/testcase.yaml
index f8caed4..948efa9 100644
--- a/tests/unit/cbprintf/testcase.yaml
+++ b/tests/unit/cbprintf/testcase.yaml
@@ -1,5 +1,5 @@
 common:
-  tags: prf
+  tags: cbprintf
   type: unit
 
 tests: