Add MSG() macro for traces

MSG() and MSG_RAW() macros are added.
They are the same as xMSG() and xMSG_RAW() existing macros, but are not
subject to dynamic trace level

Note that when the core trace level is 0, these macros are void.

This patch also fixes an issue with "printf" level.

Change-Id: Ibff6058d7e35d728a46878b345b6e0833c18aec1
Reviewed-on: https://gerrit.st.com/18102
Reviewed-by: Emmanuel MICHEL <emmanuel.michel@st.com>
Signed-off-by: Pascal Brand <pascal.brand@st.com>