logging: Kconfig cleanup of frontened related options

Cleanup in kconfig options in preparation for adding a
frontend that will use dictionary mode.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
diff --git a/subsys/logging/Kconfig.processing b/subsys/logging/Kconfig.processing
index 38b1c79..f67693b 100644
--- a/subsys/logging/Kconfig.processing
+++ b/subsys/logging/Kconfig.processing
@@ -14,11 +14,12 @@
 	int "Maximum string length supported by LOG_PRINTK"
 	depends on LOG_PRINTK
 	depends on (!LOG_MODE_IMMEDIATE || USERSPACE)
+	depends on LOG1
 	default 128
 	help
 	  Array is allocated on the stack.
 
-if !LOG_MODE_IMMEDIATE
+if LOG_MODE_DEFERRED && !LOG_FRONTEND_ONLY
 
 config LOG_MODE_OVERFLOW
 	bool "Drop oldest message when full"
@@ -106,7 +107,7 @@
 	help
 	  Number of bytes dedicated for the logger internal buffer.
 
-endif # !LOG_MODE_IMMEDIATE
+endif # LOG_MODE_DEFERRED && !LOG_FRONTEND_ONLY
 
 if LOG1_DEFERRED