mfd: Cache tps65910 register when we need it

During regmap initialization, we do not provide the default value and
hence in place of caching register during regmap_init(), cache it
when actually we need it i.e. after reading of that register.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/tps65910.c

@@ -62,8 +62,7 @@ static const struct regmap_config tps65910_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.volatile_reg = is_volatile_reg,
-	.max_register = TPS65910_MAX_REGISTER,
-	.num_reg_defaults_raw = TPS65910_MAX_REGISTER,
+	.max_register = TPS65910_MAX_REGISTER - 1,
 	.cache_type = REGCACHE_RBTREE,
 };