i2c: sprd: Fix undefined reference errors

Since the i2c driver of Spreadtrum can not be build as one module, thus
it should depend on CONFIG_I2C is build in.
Signed-off-by: Baolin Wang <baolin.wang@spreadtrum.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/Kconfig

@@ -910,7 +910,7 @@ config I2C_SIRF
 
 config I2C_SPRD
 	bool "Spreadtrum I2C interface"
-	depends on ARCH_SPRD
+	depends on I2C=y && ARCH_SPRD
 	help
 	  If you say yes to this option, support will be included for the
 	  Spreadtrum I2C interface.