net: tc: Deprecate CONFIG_NET_TC_SKIP_FOR_HIGH_PRIO

Since a separate CONFIG_NET_TC_RX_SKIP_FOR_HIGH_PRIO was introduced for
RX TC queues, CONFIG_NET_TC_SKIP_FOR_HIGH_PRIO became ambiguous,
rename it to CONFIG_NET_TC_TX_SKIP_FOR_HIGH_PRIO and deprecate the old
config.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>