iio: common: ssp_sensors: Initialize calculated_time in ssp_common_process_data

iio: common: ssp_sensors: Initialize calculated_time in ssp_common_process_data

When building with -Wsometimes-uninitialized, Clang warns:

drivers/iio/common/ssp_sensors/ssp_iio.c:95:6: warning: variable
'calculated_time' is used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]

While it isn't wrong, this will never be a problem because
iio_push_to_buffers_with_timestamp only uses calculated_time
on the same condition that it is assigned (when scan_timestamp
is not zero). While iio_push_to_buffers_with_timestamp is marked
as inline, Clang does inlining in the optimization stage, which
happens after the semantic analysis phase (plus inline is merely
a hint to the compiler).

Fix this by just zero initializing calculated_time.

Link: https://github.com/ClangBuiltLinux/linux/issues/394
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>