[RESEND PATCH -net] cpsw/netcp: cpts depends on posix_timers

[Arnd Bergmann <arnd@arndb.de>]

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]

It really makes no sense to build this driver if we can't use PTP,
so it's better to go back to 'select PTP_1588_CLOCK' but instead
add a dependency on POSIX_TIMERS. Adding 'depends on PTP_1588_CLOCK'
might also work, but has the risk of circular dependencies when
mixed with other drivers using 'imply'.

Fixes: baa73d9e478f ("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>
---
Originally submitted on Dec 16, but not applied after I missed a
reply from Nico. I confirmed that this is still needed for v4.10
and v4.11-rc2 and am resending it without changes.
---
 drivers/net/ethernet/ti/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/Kconfig b/drivers/net/ethernet/ti/Kconfig
index d42257fbe9d9..c114efcd1575 100644
--- a/drivers/net/ethernet/ti/Kconfig
+++ b/drivers/net/ethernet/ti/Kconfig
@@ -76,7 +76,8 @@ config TI_CPSW
 config TI_CPTS_ENABLE
 	bool "TI Common Platform Time Sync (CPTS) Support"
 	depends on TI_CPSW || TI_KEYSTONE_NETCP
-	imply PTP_1588_CLOCK
+	depends on POSIX_TIMERS
+	select 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.
-- 
2.9.0