ASoC: cs-amp-lib: Ignore empty UEFI calibration entries

[ Upstream commit bb4485562f5907708f1c218b5d70dce04165d1e1 ]

If the timestamp of a calibration entry is 0 it is an unused entry and
must be ignored.

Some end-products reserve EFI space for calibration entries by shipping
with a zero-filled EFI file. When searching the file for calibration
data the driver must skip the empty entries. The timestamp of a valid
entry is always non-zero.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 1cad8725

 ("ASoC: cs-amp-lib: Add helpers for factory calibration data")
Link: https://patch.msgid.link/20240822133544.304421-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>