ISL9305_MAX_REGULATOR is the last index used to access the init_data[]
array, so we need to add one to this last index to obtain the necessary
array size.

This fixes the following smatch error:

  drivers/regulator/isl9305.c:160 isl9305_i2c_probe() error: buffer overflow 'pdata->init_data' 3 <= 3

Fixes: dec38b5c ("regulator: isl9305: Add Intersil ISL9305/H driver")
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>