net: bgmac: clarify CONFIG_BCMA dependency

The bgmac driver depends on BCMA_HOST_SOC, which is only used
when CONFIG_BCMA is enabled. However, it is a bool option and can
be set when CONFIG_BCMA=m, and then bgmac can be built-in, leading
to an obvious link error:

drivers/built-in.o: In function `bgmac_init':
:(.init.text+0x7f2c): undefined reference to `__bcma_driver_register'
drivers/built-in.o: In function `bgmac_exit':
:(.exit.text+0x110a): undefined reference to `bcma_driver_unregister'

To avoid this case, we need to depend on both BCMA and BCMA_SOC,
as this patch does. I'm also trying to make the dependency more
readable by splitting it into three lines, and adding a COMPILE_TEST
alternative so we can test-build it in all configurations that
support BCMA.

The added dependency on FIXED_PHY addresses a related issue where
we cannot call fixed_phy_register() when CONFIG_FIXED_PHY=m and
CONFIG_BGMAC=y.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/Kconfig

@@ -151,8 +151,11 @@ config BNX2X_VXLAN
 
 config BGMAC
 	tristate "BCMA bus GBit core support"
-	depends on BCMA_HOST_SOC && HAS_DMA && (BCM47XX || ARCH_BCM_5301X)
+	depends on BCMA && BCMA_HOST_SOC
+	depends on HAS_DMA
+	depends on BCM47XX || ARCH_BCM_5301X || COMPILE_TEST
 	select PHYLIB
+	select FIXED_PHY
 	---help---
 	  This driver supports GBit MAC and BCM4706 GBit MAC cores on BCMA bus.
 	  They can be found on BCM47xx SoCs and provide gigabit ethernet.