dts_fixups: Use DT_ prefix in all defined labels not related to Kconfig

These changes were obtained by running a script  created by
Ulf Magnusson <Ulf.Magnusson@nordicsemi.no> for the following
specification:

1. Read the contents of all dts_fixup.h files in Zephyr
2. Check the left-hand side of the #define macros (i.e. the X in
   #define X Y)
3. Check if that name is also the name of a Kconfig option
   3.a If it is, then do nothing
   3.b If it is not, then replace CONFIG_ with DT_ or add DT_ if it
       has neither of these two prefixes
4. Replace the use of the changed #define in the code itself
   (.c, .h, .ld)

Additionally, some tweaks had to be added to this script to catch some
of the macros used in the code in a parameterized form, e.g.:
- CONFIG_GPIO_STM32_GPIO##__SUFFIX##_BASE_ADDRESS
- CONFIG_UART_##idx##_TX_PIN
- I2C_SBCON_##_num##_BASE_ADDR
and to prevent adding DT_ prefix to the following symbols:
- FLASH_START
- FLASH_SIZE
- SRAM_START
- SRAM_SIZE
- _ROM_ADDR
- _ROM_SIZE
- _RAM_ADDR
- _RAM_SIZE
which are surprisingly also defined in some dts_fixup.h files.

Finally, some manual corrections had to be done as well:
- name##_IRQ -> DT_##name##_IRQ in uart_stm32.c

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>

soc/x86/ia32/linker.ld

@@ -15,11 +15,11 @@
 #include <generated_dts_board.h>
 
 /* physical address where the kernel is loaded */
-#define PHYS_LOAD_ADDR CONFIG_PHYS_LOAD_ADDR
+#define PHYS_LOAD_ADDR DT_PHYS_LOAD_ADDR
 
 /* physical address of RAM */
 #ifdef CONFIG_XIP
-  #define PHYS_RAM_ADDR    CONFIG_PHYS_RAM_ADDR
+  #define PHYS_RAM_ADDR    DT_PHYS_RAM_ADDR
 #else  /* !CONFIG_XIP */
   #define PHYS_RAM_ADDR    PHYS_LOAD_ADDR
 #endif /* CONFIG_XIP */
@@ -27,10 +27,10 @@
 MEMORY
     {
 #ifdef CONFIG_XIP
-    ROM (rx)        : ORIGIN = PHYS_LOAD_ADDR, LENGTH = CONFIG_ROM_SIZE*1K
-    RAM (wx)        : ORIGIN = PHYS_RAM_ADDR, LENGTH = CONFIG_RAM_SIZE*1K
+    ROM (rx)        : ORIGIN = PHYS_LOAD_ADDR, LENGTH = DT_ROM_SIZE*1K
+    RAM (wx)        : ORIGIN = PHYS_RAM_ADDR, LENGTH = DT_RAM_SIZE*1K
 #else  /* !CONFIG_XIP */
-    RAM (wx)	    : ORIGIN = PHYS_LOAD_ADDR, LENGTH = CONFIG_RAM_SIZE*1K
+    RAM (wx)	    : ORIGIN = PHYS_LOAD_ADDR, LENGTH = DT_RAM_SIZE*1K
 #endif /* CONFIG_XIP */
 
     /*