x_power: Remove duplicate chg mask

Reported-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Ian Lartey <ian@opensource.wolfsonmicro.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
Tt¦0”!x