dts/arm/st/l4: don't delete the sram0 node

This commit removes the deletion of the `sram0` node, which resulted in
the compat string `mmio-sram` missing from the final devicetree when
building stm32l4r5-based platforms in Zephyr.

This bug was introduced in
306dea6.

Signed-off-by: Filip Kokosinski <[email protected]>

Author: fkokosinski

dts/arm/st/l4/stm32l4r5.dtsi

@@ -8,7 +8,6 @@
 #include <st/l4/stm32l4p5.dtsi>
 
 /delete-node/ &sdmmc2;
-/delete-node/ &sram0;
 
 / {
 	sram0: memory@20000000 {