iio: gyro: adis16060: Change the name of function.

Change the name of function from adis16060_spi_write_than_read()
to adis16060_spi_write_then_read(). change "than" to "then" as
its time depended.

Signed-off-by: simran singhal <singhalsimran0@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>