mx6slevk: Add Ethernet support

mx6slevk has a SMSC8720 connected in RMII mode.

Add support for it.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/arch/arm/include/asm/arch-mx6/clock.h b/arch/arm/include/asm/arch-mx6/clock.h
index c493687..93f29a7 100644
--- a/arch/arm/include/asm/arch-mx6/clock.h
+++ b/arch/arm/include/asm/arch-mx6/clock.h
@@ -50,4 +50,5 @@
 int enable_sata_clock(void);
 int enable_i2c_clk(unsigned char enable, unsigned i2c_num);
 void enable_ipu_clock(void);
+int enable_fec_anatop_clock(void);
 #endif /* __ASM_ARCH_CLOCK_H */