rcar: i2c: Migrate SYS_I2C_SH to Kconfig

- Migrate SYS_I2C_SH and related defines to Kconfig
- Remove currently unused SYS_I2C_SH related defines
- Cleanup related README section.

Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/i2c/sh_i2c.c b/drivers/i2c/sh_i2c.c
index 26a8700..6cecec4 100644
--- a/drivers/i2c/sh_i2c.c
+++ b/drivers/i2c/sh_i2c.c
@@ -294,20 +294,20 @@
  * Register RCAR i2c adapters
  */
 U_BOOT_I2C_ADAP_COMPLETE(sh_0, sh_i2c_init, sh_i2c_probe, sh_i2c_read,
-	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SH_SPEED0, 0, 0)
+	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SPEED, 0, 0)
 #ifdef CONFIG_SYS_I2C_SH_BASE1
 U_BOOT_I2C_ADAP_COMPLETE(sh_1, sh_i2c_init, sh_i2c_probe, sh_i2c_read,
-	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SH_SPEED1, 0, 1)
+	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SPEED, 0, 1)
 #endif
 #ifdef CONFIG_SYS_I2C_SH_BASE2
 U_BOOT_I2C_ADAP_COMPLETE(sh_2, sh_i2c_init, sh_i2c_probe, sh_i2c_read,
-	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SH_SPEED2, 0, 2)
+	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SPEED, 0, 2)
 #endif
 #ifdef CONFIG_SYS_I2C_SH_BASE3
 U_BOOT_I2C_ADAP_COMPLETE(sh_3, sh_i2c_init, sh_i2c_probe, sh_i2c_read,
-	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SH_SPEED3, 0, 3)
+	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SPEED, 0, 3)
 #endif
 #ifdef CONFIG_SYS_I2C_SH_BASE4
 U_BOOT_I2C_ADAP_COMPLETE(sh_4, sh_i2c_init, sh_i2c_probe, sh_i2c_read,
-	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SH_SPEED4, 0, 4)
+	sh_i2c_write, sh_i2c_set_bus_speed, CONFIG_SYS_I2C_SPEED, 0, 4)
 #endif