net: wangxun: fix LIBWX dependencies again

Two more drivers got added that use LIBWX and cause a build warning

WARNING: unmet direct dependencies detected for LIBWX
Depends on [m]: NETDEVICES [=y] && ETHERNET [=y] && NET_VENDOR_WANGXUN [=y] && PTP_1588_CLOCK_OPTIONAL [=m]
Selected by [y]:
- NGBEVF [=y] && NETDEVICES [=y] && ETHERNET [=y] && NET_VENDOR_WANGXUN [=y] && PCI_MSI [=y]
Selected by [m]:
- NGBE [=m] && NETDEVICES [=y] && ETHERNET [=y] && NET_VENDOR_WANGXUN [=y] && PCI [=y] && PTP_1588_CLOCK_OPTIONAL [=m]

ld: drivers/net/ethernet/wangxun/libwx/wx_lib.o: in function `wx_clean_tx_irq':
wx_lib.c:(.text+0x5a68): undefined reference to `ptp_schedule_worker'
ld: drivers/net/ethernet/wangxun/libwx/wx_ethtool.o: in function `wx_nway_reset':
wx_ethtool.c:(.text+0x880): undefined reference to `phylink_ethtool_nway_reset'

Add the same dependency on PTP_1588_CLOCK_OPTIONAL to the two driver
using this library module, following the pattern from commit
8fa19c2c69fb ("net: wangxun: fix LIBWX dependencies").

Fixes: 377d180bd71c ("net: wangxun: add txgbevf build")
Fixes: a0008a3658a3 ("net: wangxun: add ngbevf build")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Simon Horman <horms@kernel.org> # build-tested
Link: https://patch.msgid.link/20250711082339.1372821-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>