fix(stm32mp1-fdts): move /omit-if-no-ref/ to overlay files

To keep (as much as possible) alignment with Linux DT, move the
/omit-if-no-ref/ keywords to DT overlay files (fdts/stm32mp1*-bl*.dtsi).
This also ease checks for ST tools.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: Ib467a6b65f05a84c9678799ad32e1820249b4ed1
diff --git a/fdts/stm32mp13-bl2.dtsi b/fdts/stm32mp13-bl2.dtsi
index 06db796..2b23daf 100644
--- a/fdts/stm32mp13-bl2.dtsi
+++ b/fdts/stm32mp13-bl2.dtsi
@@ -3,6 +3,15 @@
  * Copyright (c) 2022-2023, STMicroelectronics - All Rights Reserved
  */
 
+/omit-if-no-ref/ &i2c4_pins_a;
+/omit-if-no-ref/ &sdmmc1_b4_pins_a;
+/omit-if-no-ref/ &sdmmc1_clk_pins_a;
+/omit-if-no-ref/ &sdmmc2_b4_pins_a;
+/omit-if-no-ref/ &sdmmc2_clk_pins_a;
+/omit-if-no-ref/ &uart4_pins_a;
+/omit-if-no-ref/ &uart8_pins_a;
+/omit-if-no-ref/ &usart1_pins_a;
+
 / {
 	aliases {
 #if !STM32MP_EMMC && !STM32MP_SDMMC