ARM: defconfig: drop CONFIG_PTP_1588_CLOCK=y

PTP support is now enabled by default for configurations with
ethernet support, so drop the redundant entries in defconfig
files.

Fixes: e5f31552 ("ethernet: fix PTP_1588_CLOCK dependencies")
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>