drivers: optee: fix i2c build issue

When the optee driver is compiled into the kernel while the i2c core
is configured as a module, the i2c symbols are not available.

This commit addresses the situation by disabling the i2c support for
this use case while allowing it in all other scenarios:

 i2c=y, optee=y
 i2c=m, optee=m
 i2c=y, optee=m
 i2c=m, optee=y (not supported)

Fixes: c05210ab ("drivers: optee: allow op-tee to access devices on the i2c bus")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/rpc.c

@@ -50,7 +50,7 @@ static void handle_rpc_func_cmd_get_time(struct optee_msg_arg *arg)
 	arg->ret = TEEC_ERROR_BAD_PARAMETERS;
 }
 
-#if IS_ENABLED(CONFIG_I2C)
+#if IS_REACHABLE(CONFIG_I2C)
 static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
 					     struct optee_msg_arg *arg)
 {