mfd: Set da903x bits if new value is different from the old one

It does not make sense to write new value only when all the bit_mask
bits are zero.
We need to write new value if the bit mask fields of new value is
not equal to old value.

Signed-off-by: Axel Lin <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/mfd/da903x.c

···
 	if (ret)
 		goto out;
 
-	if ((reg_val & bit_mask) == 0) {
+	if ((reg_val & bit_mask) != bit_mask) {
 		reg_val |= bit_mask;
 		ret = __da903x_write(chip->client, reg, reg_val);
 	}