Input: synaptics - hide unused smbus_pnp_ids[] array

When SMBUS is disabled, this is never referenced, causing a W=1 warning:

drivers/input/mouse/synaptics.c:164:27: error: 'smbus_pnp_ids' defined but not used [-Werror=unused-const-variable=]

Hide the array behind the same #ifdef as the code referencing it.

Fixes: e839ffa ("Input: synaptics - add support for Intertouch devices")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250225145451.1141995-1-arnd@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: arndb

drivers/input/mouse/synaptics.c

@@ -161,6 +161,7 @@ static const char * const topbuttonpad_pnp_ids[] = {
 	NULL
 };
 
+#ifdef CONFIG_MOUSE_PS2_SYNAPTICS_SMBUS
 static const char * const smbus_pnp_ids[] = {
 	/* all of the topbuttonpad_pnp_ids are valid, we just add some extras */
 	"LEN0048", /* X1 Carbon 3 */
@@ -196,6 +197,7 @@ static const char * const smbus_pnp_ids[] = {
 	"SYN3257", /* HP Envy 13-ad105ng */
 	NULL
 };
+#endif
 
 static const char * const forcepad_pnp_ids[] = {
 	"SYN300D",