refactor(stm32mp15-fdts): remove timers15 node

The node is currently not used in TF-A. Remove it.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Iedc4745f155ebb9c80132311a8623e4498f0689f
diff --git a/fdts/stm32mp15xx-dkx.dtsi b/fdts/stm32mp15xx-dkx.dtsi
index f1d88b3..52d4170 100644
--- a/fdts/stm32mp15xx-dkx.dtsi
+++ b/fdts/stm32mp15xx-dkx.dtsi
@@ -302,10 +302,6 @@
 	status = "okay";
 };
 
-&timers15 {
-	secure-status = "okay";
-};
-
 &uart4 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart4_pins_a>;