iio: invensense: remove redundant initialization of variable period

The variable period is being initialized with a value that is never
read, it is being re-assigned a new value later on before it is read.
The initialization is redundant and can be removed.

Cleans up clang scan build warning:
Value stored to 'period' during its initialization is never
read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Acked-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20240106153202.54861-1-colin.i.king@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>