net: ethernet: renesas: rcar_gen4_ptp: Depend on PTP_1588_CLOCK

When breaking out the Gen4 gPTP support to its own module the dependency
on the PTP_1588_CLOCK framework was left as optional and only stated for
the driver using the module. This leads to issues when doing
COMPILE_TEST of RENESAS_GEN4_PTP separately and PTP_1588_CLOCK is built
as a module and the other as a built-in. Add an explicit depend on
PTP_1588_CLOCK.

While at it remove the optional support for PTP_1588_CLOCK from
RENESAS_ETHER_SWITCH as the driver unconditionally calls the Gen4 gPTP
module and thus also requires the PTP_1588_CLOCK framework.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 8c1c6623

 ("net: ethernet: renesas: rcar_gen4_ptp: Break out to module")
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20231129111142.3322667-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Jakub Kicinski <kuba@kernel.org>