[nrf fromtree] soc: nordic: Gate FLASH_0 MPU region on CONFIG_XIP

Only include a flash MPU region if CONFIG_XIP is set, similar to
arm/core/mpu/arm_mpu_regions.c.

Signed-off-by: Josh DeWitt <josh.dewitt@garmin.com>
(cherry picked from commit 0dc2e0c)

Author: dewitt-garmin

soc/nordic/common/nrf54hx_nrf92x_mpu_regions.c

@@ -22,10 +22,12 @@
 #define SOFTPERIPH_SIZE	DT_REG_SIZE(DT_NODELABEL(softperiph_ram))
 
 static struct arm_mpu_region mpu_regions[] = {
+#ifdef CONFIG_XIP
 	MPU_REGION_ENTRY("FLASH_0",
 			 CONFIG_FLASH_BASE_ADDRESS,
 			 REGION_FLASH_ATTR(CONFIG_FLASH_BASE_ADDRESS,
 				CONFIG_FLASH_SIZE * 1024)),
+#endif
 	MPU_REGION_ENTRY("SRAM_0",
 			 CONFIG_SRAM_BASE_ADDRESS,
 			 REGION_RAM_ATTR(CONFIG_SRAM_BASE_ADDRESS,