sblim-sfcb: Fix target postinst
Separate out target specific postintalls into pkg_postinst_ontarget_PN
Fixes
/mnt/b/yoe/master/build/tmp/work/qemuarm64-yoe-linux/meta-oe-ptest-image/1.0-r0/rootfs//var/lib/opkg/info/sblim-sfcb.postinst: line 6: /usr/share/sfcb/genSslCert.sh: No such file or directory
Signed-off-by: Khem Raj <raj.khem@gmail.com>