cpsw/netcp: work around reverse cpts dependency

The dependency is reversed: cpsw and netcp call into cpts,
but cpts depends on the other two in Kconfig. This can lead
to cpts being a loadable module and its callers built-in:

drivers/net/ethernet/ti/cpsw.o: In function `cpsw_remove':
cpsw.c:(.text.cpsw_remove+0xd0): undefined reference to `cpts_release'
drivers/net/ethernet/ti/cpsw.o: In function `cpsw_rx_handler':
cpsw.c:(.text.cpsw_rx_handler+0x2dc): undefined reference to `cpts_rx_timestamp'
drivers/net/ethernet/ti/cpsw.o: In function `cpsw_tx_handler':
cpsw.c:(.text.cpsw_tx_handler+0x7c): undefined reference to `cpts_tx_timestamp'
drivers/net/ethernet/ti/cpsw.o: In function `cpsw_ndo_stop':

As a workaround, I'm introducing another Kconfig symbol to
control the compilation of cpts, while making the actual
module controlled by a silent symbol that is =y when necessary.

Fixes: 6246168b ("net: ethernet: ti: netcp: add support of cpts")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/Kconfig

@@ -74,7 +74,7 @@ config TI_CPSW
 	  will be called cpsw.
 
 config TI_CPTS
-	tristate "TI Common Platform Time Sync (CPTS) Support"
+	bool "TI Common Platform Time Sync (CPTS) Support"
 	depends on TI_CPSW || TI_KEYSTONE_NETCP
 	imply PTP_1588_CLOCK
 	---help---
@@ -83,6 +83,12 @@ config TI_CPTS
 	  The unit can time stamp PTP UDP/IPv4 and Layer 2 packets, and the
 	  driver offers a PTP Hardware Clock.
 
+config TI_CPTS_MOD
+	tristate
+	depends on TI_CPTS
+	default y if TI_CPSW=y || TI_KEYSTONE_NETCP=y
+	default m
+
 config TI_KEYSTONE_NETCP
 	tristate "TI Keystone NETCP Core Support"
 	select TI_CPSW_ALE

drivers/net/ethernet/ti/Makefile

@@ -12,7 +12,7 @@ obj-$(CONFIG_TI_DAVINCI_MDIO) += davinci_mdio.o
 obj-$(CONFIG_TI_DAVINCI_CPDMA) += davinci_cpdma.o
 obj-$(CONFIG_TI_CPSW_PHY_SEL) += cpsw-phy-sel.o
 obj-$(CONFIG_TI_CPSW_ALE) += cpsw_ale.o
-obj-$(CONFIG_TI_CPTS) += cpts.o
+obj-$(CONFIG_TI_CPTS_MOD) += cpts.o
 obj-$(CONFIG_TI_CPSW) += ti_cpsw.o
 ti_cpsw-y := cpsw.o