iio: temperature: tsys01: fix broken PROM checksum validation

iio: temperature: tsys01: fix broken PROM checksum validation

The current implementation of tsys01_crc_valid() incorrectly sums the
first word (n_prom[0]) repeatedly instead of iterating over the 8 words
retrieved from the PROM. This leads to a checksum mismatch and probe
failure on hardware.

According to the TSYS01 datasheet, the PROM consists of 8 words. A valid
check must iterate through all 8 words to verify the integrity of the
calibration data. The current driver only checks the first word 8 times.

Note: This fix was identified during a code audit and is based on
datasheet specifications. It has not been tested on real hardware.

Fixes: 43e53407f680 ("Add tsys01 meas-spec driver support")
Signed-off-by: Salah Triki <salah.triki@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>