mtd: cfi_flash: Use CONFIG_SYS_MONITOR_BASE only when defined

Make use of CONFIG_SYS_MONITOR_BASE only when available to avoid build
error when CONFIG_SYS_MONITOR_BASE is not defined.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/mtd/cfi_flash.c b/drivers/mtd/cfi_flash.c
index c59254c..0574fa6 100644
--- a/drivers/mtd/cfi_flash.c
+++ b/drivers/mtd/cfi_flash.c
@@ -178,7 +178,8 @@
 /*-----------------------------------------------------------------------
  */
 #if defined(CONFIG_ENV_IS_IN_FLASH) || defined(CONFIG_ENV_ADDR_REDUND) || \
-	(CONFIG_SYS_MONITOR_BASE >= CONFIG_SYS_FLASH_BASE)
+	(defined(CONFIG_SYS_MONITOR_BASE) && \
+	(CONFIG_SYS_MONITOR_BASE >= CONFIG_SYS_FLASH_BASE))
 static flash_info_t *flash_get_info(ulong base)
 {
 	int i;
@@ -2329,7 +2330,8 @@
 #endif
 
 	/* Monitor protection ON by default */
-#if (CONFIG_SYS_MONITOR_BASE >= CONFIG_SYS_FLASH_BASE) && \
+#if defined(CONFIG_SYS_MONITOR_BASE) && \
+	(CONFIG_SYS_MONITOR_BASE >= CONFIG_SYS_FLASH_BASE) && \
 	(!defined(CONFIG_MONITOR_IS_IN_RAM))
 	flash_protect(FLAG_PROTECT_SET,
 		      CONFIG_SYS_MONITOR_BASE,