[nrf fromlist] soc: nordic: Disable cache for soft peripheral RAM region in nRF54H/nRF92

Add an entry for the RAM region assigned to soft peripherals that will
disable caching for that region. Without this, communication with the
FLPR coprocessor cannot be performed correctly.

Upstream PR #: 88169

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

Author: anangl

soc/nordic/common/nrf54hx_nrf92x_mpu_regions.c

@@ -18,6 +18,9 @@
 #define CAN121_SIZE	DT_REG_SIZE_BY_NAME(DT_NODELABEL(can121), message_ram) + \
 			DT_REG_SIZE_BY_NAME(DT_NODELABEL(can121), m_can)
 
+#define SOFTPERIPH_BASE	DT_REG_ADDR(DT_NODELABEL(softperiph_ram))
+#define SOFTPERIPH_SIZE	DT_REG_SIZE(DT_NODELABEL(softperiph_ram))
+
 static struct arm_mpu_region mpu_regions[] = {
 	MPU_REGION_ENTRY("FLASH_0",
 			 CONFIG_FLASH_BASE_ADDRESS,
@@ -40,6 +43,10 @@ static struct arm_mpu_region mpu_regions[] = {
 	MPU_REGION_ENTRY("CAN121_MCAN", CAN121_BASE,
 			 REGION_RAM_NOCACHE_ATTR(CAN121_BASE, CAN121_SIZE)),
 #endif
+#if DT_NODE_EXISTS(DT_NODELABEL(softperiph_ram))
+	MPU_REGION_ENTRY("SOFTPERIPH_RAM", SOFTPERIPH_BASE,
+			 REGION_RAM_NOCACHE_ATTR(SOFTPERIPH_BASE, SOFTPERIPH_SIZE)),
+#endif
 };
 
 const struct arm_mpu_config mpu_config = {