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/configs/ls2081ardb_defconfig b/configs/ls2081ardb_defconfig
index ad32df7..42ccf3f 100644
--- a/configs/ls2081ardb_defconfig
+++ b/configs/ls2081ardb_defconfig
@@ -41,6 +41,7 @@
 CONFIG_SATA_CEVA=y
 CONFIG_FSL_CAAM=y
 CONFIG_SYS_I2C_LEGACY=y
+CONFIG_SYS_I2C_EARLY_INIT=y
 CONFIG_SYS_I2C_EEPROM_ADDR=0x57
 CONFIG_FSL_ESDHC=y
 CONFIG_MTD=y