i2c: fsl_i2c: Migrate to Kconfig

- As there are no boards that use different values for speed / slave on
  different buses, use a single option.
- Switch to using the common SYS_I2C_SPEED / SYS_I2C_SLAVE options.
- Introduce _HAS_ options for additional buses as only the first one is
  common to all users.
- Convert all remaining symbols to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/am335x_shc_netboot_defconfig b/configs/am335x_shc_netboot_defconfig
index d7058f9..5481aa4 100644
--- a/configs/am335x_shc_netboot_defconfig
+++ b/configs/am335x_shc_netboot_defconfig
@@ -54,7 +54,7 @@
 CONFIG_BOOTP_SEND_HOSTNAME=y
 CONFIG_SYS_I2C_LEGACY=y
 CONFIG_SPL_SYS_I2C_LEGACY=y
-CONFIG_SYS_I2C_SLAVE=1
+CONFIG_SYS_I2C_SLAVE=0x1
 CONFIG_SYS_I2C_SPEED=400000
 CONFIG_MMC_OMAP_HS=y
 CONFIG_PHY_ADDR_ENABLE=y