iio: imu: inv_mpu6050: add all signal path resets at init

Old chips using spi require for a full reset to manually reset
all signal path. This does not harm when using i2c so do it
inconditionally. Exclude i2c only chips.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>