net: broadcom: Drop OF dependency from BGMAC_PLATFORM

All of the OF code that is used has stubbed and will compile and link
just fine, keeping COMPILE_TEST is enough.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20210106191546.1358324-1-f.fainelli@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/Kconfig

@@ -174,7 +174,6 @@ config BGMAC_BCMA
 config BGMAC_PLATFORM
 	tristate "Broadcom iProc GBit platform support"
 	depends on ARCH_BCM_IPROC || COMPILE_TEST
-	depends on OF
 	select BGMAC
 	select PHYLIB
 	select FIXED_PHY