net/stmmac: mark probe function as __devinit

Driver probe functions are generally __devinit so they will be
discarded after initialization for non-hotplug kernels.
This was found by a new warning after patch 6a228452d "stmmac: Add
device-tree support" adds a new __devinit function that is called
from stmmac_pltfr_probe.

Without this patch, building socfpga_defconfig results in:

WARNING: drivers/net/ethernet/stmicro/stmmac/stmmac.o(.text+0x5d4c): Section mismatch in reference from the function stmmac_pltfr_probe() to the function .devinit.text:stmmac_probe_config_dt()
The function stmmac_pltfr_probe() references
the function __devinit stmmac_probe_config_dt().
This is often because stmmac_pltfr_probe lacks a __devinit
annotation or the annotation of stmmac_probe_config_dt is wrong.

Signed-off-by: Arnd Bergmann <[e-mail]>
Cc: Stefan Roese <[e-mail]>
Cc: Giuseppe Cavallaro <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: [e-mail]
Acked-by: Stefan Roese <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

···
  * the necessary resources and invokes the main to init
  * the net device, register the mdio bus etc.
  */
-static int stmmac_pltfr_probe(struct platform_device *pdev)
+static int __devinit stmmac_pltfr_probe(struct platform_device *pdev)
 {
 	int ret = 0;
 	struct resource *res;