drivers/iio: Remove all strcpy() uses

drivers/iio: Remove all strcpy() uses

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. So, remove all the uses and add
devm_kstrdup() or devm_kasprintf() instead.

Also, modify the "for" loop conditions to clarify the access to the
st->orientation.rotation buffer.

This patch is an effort to clean up the proliferation of str*()
functions in the kernel and a previous step in the path to remove
the strcpy function from the kernel entirely [1].

[1] https://github.com/KSPP/linux/issues/88

Signed-off-by: Len Baker <len.baker@gmx.com>
Link: https://lore.kernel.org/r/20210815174204.126593-1-len.baker@gmx.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>