brcm47xx: add missing config symbol

target/linux/brcm47xx/mips74k/config-default

@@ -1,6 +1,7 @@
 # CONFIG_ADM6996_PHY is not set
 # CONFIG_BCM47XX_SSB is not set
 CONFIG_BGMAC=y
+CONFIG_BGMAC_BCMA=y
 CONFIG_BOUNCE=y
 # CONFIG_CPU_MIPS32_R1 is not set
 # CONFIG_CPU_MIPSR1 is not set

target/linux/brcm47xx/modules.mk

@@ -7,7 +7,7 @@
 
 define KernelPackage/bgmac
   TITLE:=Broadcom bgmac driver
-  KCONFIG:=CONFIG_BGMAC
+  KCONFIG:=CONFIG_BGMAC CONFIG_BGMAC_BCMA
   DEPENDS:=@TARGET_brcm47xx @!TARGET_brcm47xx_legacy
   SUBMENU:=$(NETWORK_DEVICES_MENU)
   FILES:=$(LINUX_DIR)/drivers/net/ethernet/broadcom/bgmac.ko