tests: i2c_emul: drop the array designators

Drop the array dasignators as they generate a

warning: array designators are a C99 extension

warning when compiling with clang. Not too sure if this is an actual
problem or if the warning should be disabled instead but since it's just
a test it should be fine to just drop them.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

Author: fabiobaltieri

tests/drivers/i2c/i2c_emul/src/emulated_target.cpp

@@ -25,7 +25,7 @@ DT_FOREACH_PROP_ELEM(CONTROLLER_LABEL, forwards, DEFINE_FAKE_TARGET_FUNCTION);
 
 /* clang-format off */
 #define DEFINE_EMULATED_CALLBACK(node_id, prop, n)                                                 \
-	[n] = {                                                                                    \
+	{                                                                                          \
 		.write_requested = target_write_requested_##n,                                     \
 		.read_requested = target_read_requested_##n,                                       \
 		.write_received = target_write_received_##n,                                       \
@@ -42,7 +42,7 @@ struct i2c_target_callbacks emulated_callbacks[FORWARD_COUNT] = {
 	DT_FOREACH_PROP_ELEM(CONTROLLER_LABEL, forwards, DEFINE_EMULATED_CALLBACK)};
 
 #define DEFINE_EMULATED_TARGET_CONFIG(node_id, prop, n)                                            \
-	[n] = {                                                                                    \
+	{                                                                                          \
 		.flags = 0,                                                                        \
 		.address = DT_PHA_BY_IDX(node_id, prop, n, addr),                                  \
 		.callbacks = &emulated_callbacks[n],                                               \