power: rt9455: hide unused rt9455_boost_voltage_values

The rt9455_boost_voltage_values[] array is only used when USB PHY
support is enabled, causing a W=1 warning otherwise:

drivers/power/supply/rt9455_charger.c:200:18: error: 'rt9455_boost_voltage_values' defined but not used [-Werror=unused-const-variable=]

Enclose the definition in the same #ifdef as the references to it.

Fixes: e86d69dd786e ("power_supply: Add support for Richtek RT9455 battery charger")
Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/rt9455_charger.c

···
 	4450000, 4450000, 4450000, 4450000, 4450000, 4450000, 4450000, 4450000
 };
 
+#if IS_ENABLED(CONFIG_USB_PHY)
 /*
  * When the charger is in boost mode, REG02[7:2] represent boost output
  * voltage.
···
 	5600000, 5600000, 5600000, 5600000, 5600000, 5600000, 5600000, 5600000,
 	5600000, 5600000, 5600000, 5600000, 5600000, 5600000, 5600000, 5600000,
 };
+#endif
 
 /* REG07[3:0] (VMREG) in uV */
 static const int rt9455_vmreg_values[] = {