iproute2: use tc package variant to limit other package sizes

iproute2: use tc package variant to limit other package sizes

Replace the old 'tc' with a singleton package variant which will be used
to enable additional functionality and limit it only to tc. Non-variant
packages will only be installed during 'tiny' variant builds, hence will
be configured without extra features, thus preserving previously limited
functionality and reduced package sizes.

Also set ip-tiny as the default variant, and install 'tiny' versions of
development libraries.

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>