ptp: fix kconfig dependency warnings

ptp: fix kconfig dependency warnings

Fix kconfig warnings:

PTP_1588_CLOCK selects NET_PTP_CLASSIFY, which depends on NET,
so PTP_1588_CLOCK should also depend on NET.

PTP_1588_CLOCK_PCH selects PTP_1588_CLOCK so the former should
depend on NET.

warning: (IXP4XX_ETH && PTP_1588_CLOCK) selects NET_PTP_CLASSIFY which has unmet direct dependencies (NET)

warning: (SFC && TILE_NET && BFIN_MAC_USE_HWSTAMP && TIGON3 && FEC && E1000E && IGB && IXGBE && I40E && MLX4_EN && SXGBE_ETH && STMMAC_ETH && TI_CPTS && PTP_1588_CLOCK_GIANFAR && PTP_1588_CLOCK_IXP46X && DP83640_PHY && PTP_1588_CLOCK_PCH) selects PTP_1588_CLOCK which has unmet direct dependencies (NET)
[This warning is caused by the new 'depends on NET' in PTP_1588_CLOCK.]

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>