legacy: add missing select

When adding a boolean option to legacy, it should slect BR2_LEGACY, to
trigger the legacy warning.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Config.in.legacy

@@ -149,6 +149,7 @@ config BR2_PACKAGE_PHP_SAPI_CLI_CGI
 	bool "PHP CGI and CLI options are now seperate"
 	select BR2_PACKAGE_PHP_SAPI_CLI
 	select BR2_PACKAGE_PHP_SAPI_CGI
+	select BR2_LEGACY
 	help
 	  The PHP Interface options have been split up into a
 	  separate option for each interface.
@@ -157,6 +158,7 @@ config BR2_PACKAGE_PHP_SAPI_CLI_FPM
 	bool "PHP CLI and FPM options are now separate"
 	select BR2_PACKAGE_PHP_SAPI_CLI
 	select BR2_PACKAGE_PHP_SAPI_FPM
+	select BR2_LEGACY
 	help
 	  The PHP Interface options have been split up into a
 	  separate option for each interface.