net: broadcom: BCM4908_ENET should not default to y, unconditionally

Merely enabling compile-testing should not enable additional code.
To fix this, restrict the automatic enabling of BCM4908_ENET to
ARCH_BCM4908.

Fixes: 4feffead ("net: broadcom: bcm4908enet: add BCM4908 controller driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/Kconfig

@@ -54,7 +54,7 @@ config B44_PCI
 config BCM4908_ENET
 	tristate "Broadcom BCM4908 internal mac support"
 	depends on ARCH_BCM4908 || COMPILE_TEST
-	default y
+	default y if ARCH_BCM4908
 	help
 	  This driver supports Ethernet controller integrated into Broadcom
 	  BCM4908 family SoCs.