boards: stm32n6: Clean up clocks props for xspi controllers

These props are providing default clock configuration.
Not required at boards level, clean them up.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>

Author: erwango

boards/st/nucleo_n657x0_q/nucleo_n657x0_q_common.dtsi

@@ -283,9 +283,6 @@ zephyr_udc0: &usbotg_hs1 {
 		     &xspim_p2_io3_pn5 &xspim_p2_io4_pn8 &xspim_p2_io5_pn9
 		     &xspim_p2_io6_pn10 &xspim_p2_io7_pn11>;
 	pinctrl-names = "default";
-	clocks = <&rcc STM32_CLOCK(AHB5, 12)>,
-		 <&rcc STM32_SRC_HCLK5 XSPI2_SEL(0)>,
-		 <&rcc STM32_CLOCK(AHB5, 13)>;
 	status = "okay";
 
 	mx25um51245g: ospi-nor-flash@0 {

boards/st/stm32n6570_dk/stm32n6570_dk_common.dtsi

@@ -375,9 +375,6 @@ zephyr_udc0: &usbotg_hs1 {
 		     &xspim_p1_io12_pp12 &xspim_p1_io13_pp13 &xspim_p1_io14_pp14
 		     &xspim_p1_io15_pp15>;
 	pinctrl-names = "default";
-	clocks = <&rcc STM32_CLOCK(AHB5, 5)>,
-		 <&rcc STM32_SRC_HCLK5 XSPI1_SEL(0)>,
-		 <&rcc STM32_CLOCK(AHB5, 13)>;
 	status = "okay";
 
 	memc: aps256xxn_obr: memory@0 {
@@ -402,9 +399,6 @@ zephyr_udc0: &usbotg_hs1 {
 		     &xspim_p2_io3_pn5 &xspim_p2_io4_pn8 &xspim_p2_io5_pn9
 		     &xspim_p2_io6_pn10 &xspim_p2_io7_pn11>;
 	pinctrl-names = "default";
-	clocks = <&rcc STM32_CLOCK(AHB5, 12)>,
-		 <&rcc STM32_SRC_HCLK5 XSPI2_SEL(0)>,
-		 <&rcc STM32_CLOCK(AHB5, 13)>;
 	status = "okay";
 
 	mx66uw1g45g: ospi-nor-flash@0 {