render_font.py script now uses 'PIL' and no more 'wand'.

Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@foss.st.com>
Change-Id: Iecfd3c89651ab7e32dfef16607dde1f3265dc040
Reviewed-on: https://gerrit.st.com/c/mpu/oe/optee/optee_os/+/220450
Tested-by: Nicolas TOROMANOFF <nicolas.toromanoff@st.com>
Reviewed-by: Nicolas TOROMANOFF <nicolas.toromanoff@st.com>
Reviewed-by: CIBUILD <MDG-smet-aci-builds@list.st.com>
Reviewed-by: Lionel DEBIEVE <lionel.debieve@foss.st.com>