lmb: Rename LMB_LIMIT_DMA_BELOW_4G to LMB_LIMIT_DMA_BELOW_RAM_TOP

Rename LMB_LIMIT_DMA_BELOW_4G to LMB_LIMIT_DMA_BELOW_RAM_TOP
to make the Kconfig option more descriptive. No functional
change.

Suggested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

lib/Kconfig

@@ -1295,13 +1295,14 @@ config SPL_LMB_ARCH_MEM_MAP
 	  memory map. Enable this config in such scenarios which allow
 	  architectures and boards to define their own memory map.
 
-config LMB_LIMIT_DMA_BELOW_4G
+config LMB_LIMIT_DMA_BELOW_RAM_TOP
 	bool
 	depends on LMB
 	default y if ARCH_BCM283X
 	help
-	  Some architectures can not DMA above 4 GiB boundary,
-	  limit available memory to memory below 4 GiB boundary.
+	  Some architectures can not DMA above ram_top boundary,
+	  which is after 4 GiB or 32-bit boundary too. Limit the
+	  available memory to memory below ram_top boundary.
 
 config PHANDLE_CHECK_SEQ
 	bool "Enable phandle check while getting sequence number"

lib/lmb.c

@@ -628,7 +628,7 @@ static void lmb_add_memory(void)
 
 		if (size) {
 			lmb_add(bd->bi_dram[i].start, size);
-			if (!IS_ENABLED(CONFIG_LMB_LIMIT_DMA_BELOW_4G))
+			if (!IS_ENABLED(CONFIG_LMB_LIMIT_DMA_BELOW_RAM_TOP))
 				continue;
 
 			bank_end = bd->bi_dram[i].start + size;