power: twl4030: Add twl4030_i2c_read() function

Function twl4030_i2c_read() is like twl4030_i2c_read_u8() but instead of
single value it rather returns array of values.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>