dsa: change "select" to "depends on" for NET_SWITCHDEV and for NET_DSA

This would fix randconfig compile error:
net/built-in.o: In function `netdev_switch_fib_ipv4_abort':
(.text+0xf7811): undefined reference to `fib_flush_external'

Also it fixes following warnings:
warning: (NET_DSA) selects NET_SWITCHDEV which has unmet direct dependencies (NET && INET)

warning: (NET_DSA_MV88E6060 && NET_DSA_MV88E6131 && NET_DSA_MV88E6123_61_65 && NET_DSA_MV88E6171 && NET_DSA_MV88E6352 && NET_DSA_BCM_SF2) selects NET_DSA which has unmet direct dependencies (NET && HAVE_NET_DSA && NET_SWITCHDEV)
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/Kconfig

@@ -7,7 +7,7 @@ config NET_DSA_MV88E6XXX
 
 config NET_DSA_MV88E6060
 	tristate "Marvell 88E6060 ethernet switch chip support"
-	select NET_DSA
+	depends on NET_DSA
 	select NET_DSA_TAG_TRAILER
 	---help---
 	  This enables support for the Marvell 88E6060 ethernet switch
@@ -19,7 +19,7 @@ config NET_DSA_MV88E6XXX_NEED_PPU
 
 config NET_DSA_MV88E6131
 	tristate "Marvell 88E6085/6095/6095F/6131 ethernet switch chip support"
-	select NET_DSA
+	depends on NET_DSA
 	select NET_DSA_MV88E6XXX
 	select NET_DSA_MV88E6XXX_NEED_PPU
 	select NET_DSA_TAG_DSA
@@ -29,7 +29,7 @@ config NET_DSA_MV88E6131
 
 config NET_DSA_MV88E6123_61_65
 	tristate "Marvell 88E6123/6161/6165 ethernet switch chip support"
-	select NET_DSA
+	depends on NET_DSA
 	select NET_DSA_MV88E6XXX
 	select NET_DSA_TAG_EDSA
 	---help---
@@ -38,7 +38,7 @@ config NET_DSA_MV88E6123_61_65
 
 config NET_DSA_MV88E6171
 	tristate "Marvell 88E6171/6172 ethernet switch chip support"
-	select NET_DSA
+	depends on NET_DSA
 	select NET_DSA_MV88E6XXX
 	select NET_DSA_TAG_EDSA
 	---help---
@@ -47,7 +47,7 @@ config NET_DSA_MV88E6171
 
 config NET_DSA_MV88E6352
 	tristate "Marvell 88E6176/88E6352 ethernet switch chip support"
-	select NET_DSA
+	depends on NET_DSA
 	select NET_DSA_MV88E6XXX
 	select NET_DSA_TAG_EDSA
 	---help---
@@ -56,8 +56,7 @@ config NET_DSA_MV88E6352
 
 config NET_DSA_BCM_SF2
 	tristate "Broadcom Starfighter 2 Ethernet switch support"
-	depends on HAS_IOMEM
-	select NET_DSA
+	depends on HAS_IOMEM && NET_DSA
 	select NET_DSA_TAG_BRCM
 	select FIXED_PHY
 	select BCM7XXX_PHY

net/dsa/Kconfig

@@ -6,9 +6,8 @@ config HAVE_NET_DSA
 
 config NET_DSA
 	tristate
-	depends on HAVE_NET_DSA
+	depends on HAVE_NET_DSA && NET_SWITCHDEV
 	select PHYLIB
-	select NET_SWITCHDEV
 
 if NET_DSA