samples: nrf53_sync_rtc: Move shared memory buffer next to .data

To avoid possible linker warnings, when the linker may end up placing
this section in a segment with text and therefore with execute
permissions, with let's move it next to the .data section.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

samples/boards/nrf/nrf53_sync_rtc/src/main.c

@@ -17,7 +17,7 @@ LOG_MODULE_REGISTER(main);
 /* For simulation, we can define shared memory variables linkable from
  * other MCUs just by using NATIVE_SIMULATOR_IF
  */
-NATIVE_SIMULATOR_IF uint32_t shared_cell_buffer;
+NATIVE_SIMULATOR_IF_DATA uint32_t shared_cell_buffer;
 static uint32_t shared_cell = (uintptr_t)&shared_cell_buffer;
 #else
 static uint32_t shared_cell = 0x20070000;