ldap: Add distro feature for LDAP

LDAP related packages will be pulled into the
image depending on the distro feature.

Enabling this feature increases the image size by ~500KB
as it brings nss-pam-ldapd, openldap, and nscd into the image.

(From meta-phosphor rev: b40b3f9b8c9f362583a5edcb6a64f0d3304dad5b)

Change-Id: I92ec1d2c20adfa08a87265d85962cb0390e0c854
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-phosphor/conf/distro/include/phosphor-base.inc b/meta-phosphor/conf/distro/include/phosphor-base.inc
index 3947f36..24ce8dc 100644
--- a/meta-phosphor/conf/distro/include/phosphor-base.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-base.inc
@@ -117,6 +117,7 @@
         pam \
         slp \
         systemd \
+        ldap \
         "
 
 DISTRO_FEATURES = " \