Convert CONFIG_SYS_I2C_EARLY_INIT to Kconfig

Convert SYS_I2C_EARLY_INIT to Kconfig, and make it depend on
SPL_SYS_I2C_LEGACY.  Remove the weak implementation as it's either
something that needs to exist for real, or shouldn't be called.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/freescale/ls2080aqds/ls2080aqds.c b/board/freescale/ls2080aqds/ls2080aqds.c
index c48b01f..62658c4 100644
--- a/board/freescale/ls2080aqds/ls2080aqds.c
+++ b/board/freescale/ls2080aqds/ls2080aqds.c
@@ -241,7 +241,7 @@
 
 int board_early_init_f(void)
 {
-#ifdef CONFIG_SYS_I2C_EARLY_INIT
+#if defined(CONFIG_SYS_I2C_EARLY_INIT)
 	i2c_early_init_f();
 #endif
 	fsl_lsch3_early_init_f();