iio: gyro: mpu3050: Fix alignment and size issues with buffers.

Fix a set of closely related issues.
1. When using fifo_values() there was not enough space for the timestamp to
   be inserted by iio_push_to_buffers_with_timestamp()
2. fifo_values() did not meet the alignment requirement of
   iio_push_to_buffers_with_timestamp()
3. hw_values did not meet the alignment requirement either.

1 and 2 fixed by using new iio_push_to_buffers_with_ts_unaligned() which has
no alignment or space padding requirements.
3 fixed by introducing a structure that makes the space and alignment
requirements explicit.

Fixes: 3904b28e ("iio: gyro: Add driver for the MPU-3050 gyroscope")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210613151039.569883-4-jic23@kernel.org