postgresql: propagate BR2_USE_MMU dependency to Config.in comment

The BR2_PACKAGE_POSTGRESQL option depends on BR2_USE_MMU, so the
Config.in comment about the dynamic library dependency should only be
displayed if the BR2_USE_MMU requirement is met.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/postgresql/Config.in

@@ -19,4 +19,5 @@ config BR2_PACKAGE_POSTGRESQL
 	  http://www.postgresql.org
 
 comment "postgresql needs a toolchain w/ dynamic library"
+	depends on BR2_USE_MMU
 	depends on BR2_STATIC_LIBS