net: dsa: sja1105: fix ptp link error

Due to a reversed dependency, it is possible to build
the lower ptp driver as a loadable module and the actual
driver using it as built-in, causing a link error:

drivers/net/dsa/sja1105/sja1105_spi.o: In function `sja1105_static_config_upload':
sja1105_spi.c:(.text+0x6f0): undefined reference to `sja1105_ptp_reset'
drivers/net/dsa/sja1105/sja1105_spi.o:(.data+0x2d4): undefined reference to `sja1105et_ptp_cmd'
drivers/net/dsa/sja1105/sja1105_spi.o:(.data+0x604): undefined reference to `sja1105pqrs_ptp_cmd'
drivers/net/dsa/sja1105/sja1105_main.o: In function `sja1105_remove':
sja1105_main.c:(.text+0x8d4): undefined reference to `sja1105_ptp_clock_unregister'
drivers/net/dsa/sja1105/sja1105_main.o: In function `sja1105_rxtstamp_work':
sja1105_main.c:(.text+0x964): undefined reference to `sja1105_tstamp_reconstruct'
drivers/net/dsa/sja1105/sja1105_main.o: In function `sja1105_setup':
sja1105_main.c:(.text+0xb7c): undefined reference to `sja1105_ptp_clock_register'
drivers/net/dsa/sja1105/sja1105_main.o: In function `sja1105_port_deferred_xmit':
sja1105_main.c:(.text+0x1fa0): undefined reference to `sja1105_ptpegr_ts_poll'
sja1105_main.c:(.text+0x1fc4): undefined reference to `sja1105_tstamp_reconstruct'
drivers/net/dsa/sja1105/sja1105_main.o:(.rodata+0x5b0): undefined reference to `sja1105_get_ts_info'

Change the Makefile logic to always build the ptp module
the same way as the rest. Another option would be to
just add it to the same module and remove the exports,
but I don't know if there was a good reason to keep them
separate.

Fixes: bb77f36a ("net: dsa: sja1105: Add support for the PTP clock")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/Kconfig

@@ -18,7 +18,7 @@ tristate "NXP SJA1105 Ethernet switch family support"
 	    - SJA1105S (Gen. 2, SGMII, TT-Ethernet)
 
 config NET_DSA_SJA1105_PTP
-tristate "Support for the PTP clock on the NXP SJA1105 Ethernet switch"
+	bool "Support for the PTP clock on the NXP SJA1105 Ethernet switch"
 	depends on NET_DSA_SJA1105
 	help
 	  This enables support for timestamping and PTP clock manipulations in

drivers/net/dsa/sja1105/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_NET_DSA_SJA1105) += sja1105.o
-obj-$(CONFIG_NET_DSA_SJA1105_PTP) += sja1105_ptp.o
 
 sja1105-objs := \
     sja1105_spi.o \
@@ -9,3 +8,7 @@ sja1105-objs := \
     sja1105_clocking.o \
     sja1105_static_config.o \
     sja1105_dynamic_config.o \
+
+ifdef CONFIG_NET_DSA_SJA1105_PTP
+obj-$(CONFIG_NET_DSA_SJA1105) += sja1105_ptp.o
+endif