php7: move into own submenu to prepare for upcoming php8

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

lang/php7/Makefile

@@ -47,7 +47,7 @@ include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/nls.mk
 
 define Package/php7/Default
-  SUBMENU:=PHP
+  SUBMENU:=PHP7
   SECTION:=lang
   CATEGORY:=Languages
   TITLE:=PHP7 Hypertext preprocessor

lang/php7/pecl.mk

@@ -4,7 +4,7 @@
 #
 
 define Package/php7-pecl/Default
-  SUBMENU:=PHP
+  SUBMENU:=PHP7
   SECTION:=lang
   CATEGORY:=Languages
   URL:=http://pecl.php.net/