stmmac: fix driver built w/ w/o both pci and platf modules

The commit ba27ec66ffeb78cbf fixes the Kconfig of the
driver when built as module allowing to select/unselect
the PCI and Platform modules that are not anymore mutually
exclusive. This patch fixes and guarantees that the driver
builds on all the platforms w/ w/o PCI and when select/unselect
the two stmmac supports. In case of there are some problems
on both the configuration and the pci/pltf registration the
module_init will fail.

v2: set the CONFIG_STMMAC_PLATFORM enabled by default.
I've just noticed that this can actually help on
some configurations that don't enable any STMMAC
options by default (e.g. SPEAr).

v3: change printk level when do not register the driver.

Reported-by: Fengguang Wu <wfg@linux.intel.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/stmicro/stmmac/Kconfig b/drivers/net/ethernet/stmicro/stmmac/Kconfig
index 0076f77..9f44827 100644
--- a/drivers/net/ethernet/stmicro/stmmac/Kconfig
+++ b/drivers/net/ethernet/stmicro/stmmac/Kconfig
@@ -15,6 +15,7 @@
 config STMMAC_PLATFORM
 	bool "STMMAC Platform bus support"
 	depends on STMMAC_ETH
+	default y
 	---help---
 	  This selects the platform specific bus support for
 	  the stmmac device driver. This is the driver used