iio: accel: bma400: Fix uninitialized variable field_value in tap event handling.

BugLink: https://bugs.launchpad.net/bugs/2097575

[ Upstream commit db9795a ]

In the current implementation, the local variable field_value is used
without prior initialization, which may lead to reading uninitialized
memory. Specifically, in the macro set_mask_bits, the initial
(potentially uninitialized) value of the buffer is copied into old__,
and a mask is applied to calculate new__. A similar issue was resolved in
commit 6ee2a70 ("iio: accel: bma400: Fix smatch warning based on use
of unintialized value.").

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 961db2d ("iio: accel: bma400: Add support for single and double tap events")
Signed-off-by: Mikhail Lobanov <m.lobanov@rosalinux.ru>
Link: https://patch.msgid.link/20240910083624.27224-1-m.lobanov@rosalinux.ru
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: Mikhail Lobanov

drivers/iio/accel/bma400_core.c

@@ -1219,7 +1219,8 @@ static int bma400_activity_event_en(struct bma400_data *data,
 static int bma400_tap_event_en(struct bma400_data *data,
 			       enum iio_event_direction dir, int state)
 {
-	unsigned int mask, field_value;
+	unsigned int mask;
+	unsigned int field_value = 0;
 	int ret;
 
 	/*