cpsw/netcp: cpts depends on posix_timers

With posix timers having become optional, we get a build error with
the cpts time sync option of the CPSW driver:

drivers/net/ethernet/ti/cpts.c: In function 'cpts_find_ts':
drivers/net/ethernet/ti/cpts.c:291:23: error: implicit declaration of function 'ptp_classify_raw';did you mean 'ptp_classifier_init'? [-Werror=implicit-function-declaration]

This adds a hard dependency on PTP_CLOCK to avoid the problem, as
building it without PTP support makes no sense anyway.

Fixes: baa73d9e ("posix-timers: Make them configurable")
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/Kconfig

@@ -76,7 +76,7 @@ config TI_CPSW
 config TI_CPTS
 	bool "TI Common Platform Time Sync (CPTS) Support"
 	depends on TI_CPSW || TI_KEYSTONE_NETCP
-	imply PTP_1588_CLOCK
+	depends on PTP_1588_CLOCK
 	---help---
 	  This driver supports the Common Platform Time Sync unit of
 	  the CPSW Ethernet Switch and Keystone 2 1g/10g Switch Subsystem.