net: ti: icssg-prueth: add PTP_1588_CLOCK_OPTIONAL dependency

The new icssg-prueth driver needs the same dependency as the other parts
that use the ptp-1588:

WARNING: unmet direct dependencies detected for TI_ICSS_IEP
  Depends on [m]: NETDEVICES [=y] && ETHERNET [=y] && NET_VENDOR_TI [=y] && PTP_1588_CLOCK_OPTIONAL [=m] && TI_PRUSS [=y]
  Selected by [y]:
  - TI_PRUETH [=y] && NETDEVICES [=y] && ETHERNET [=y] && NET_VENDOR_TI [=y] && PRU_REMOTEPROC [=y] && NET_SWITCHDEV [=y]

Add the correct dependency on the two drivers missing it, and remove
the pointless 'imply' in the process.

Fixes: e654b85 ("net: ti: icssg-prueth: Add ICSSG Ethernet driver for AM65x SR1.0 platforms")
Fixes: 511f6c1 ("net: ti: icssm-prueth: Adds ICSSM Ethernet driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20251204100138.1034175-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: arndb

drivers/net/ethernet/ti/Kconfig

@@ -209,6 +209,7 @@ config TI_ICSSG_PRUETH_SR1
 	depends on PRU_REMOTEPROC
 	depends on NET_SWITCHDEV
 	depends on ARCH_K3 && OF && TI_K3_UDMA_GLUE_LAYER
+	depends on PTP_1588_CLOCK_OPTIONAL
 	help
 	  Support dual Gigabit Ethernet ports over the ICSSG PRU Subsystem.
 	  This subsystem is available on the AM65 SR1.0 platform.
@@ -234,7 +235,7 @@ config TI_PRUETH
 	depends on PRU_REMOTEPROC
 	depends on NET_SWITCHDEV
 	select TI_ICSS_IEP
-	imply PTP_1588_CLOCK
+	depends on PTP_1588_CLOCK_OPTIONAL
 	help
 	  Some TI SoCs has Programmable Realtime Unit (PRU) cores which can
 	  support Single or Dual Ethernet ports with the help of firmware code