iio: sx9310: Fix write_.._debounce()

iio: sx9310: Fix write_.._debounce()

Check input to be sure it matches Semtech sx9310 specification and
can fit into debounce register.
Compare argument writen to thresh_.._period with read from same
sysfs attribute:

Before:                   Afer:
write   |  read           write   |  read
-1      |     8           -1 fails: -EINVAL
0       |     8           0       |     0
1       |     0           1       |     0
2..15   |  2^log2(N)      2..15   |  2^log2(N)
16      |     0           >= 16 fails: -EINVAL

Fixes: 1b6872015f0b ("iio: sx9310: Support setting debounce values")
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Cc: stable@vger.kernel.org
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20210331182222.219533-1-gwendal@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>