power: supply: qcom_battmgr: terminate the strings from firmware

The qcom_battmgr_sc8280xp_strcpy() takes a Pascal-style string when the
firmware sends one. Otherwise it copies all BATTMGR_STRING_LEN bytes and
leaves the destination without a terminator.

Those destinations are model_number, serial_number and oem_info, each
BATTMGR_STRING_LEN and declared next to each other. They go out to user
space as val->strval, which power_supply_format_property() prints with
"%s", so a firmware string that fills the whole field makes that read run
into the following members.

Use strscpy() so the copy always terminates, the way the SM8350 path
already does for the same field.

Fixes: 29e8142b56 ("power: supply: Introduce Qualcomm PMIC GLINK power supply")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Link: https://patch.msgid.link/20260727074119.2585463-1-sammiee5311@gmail.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/qcom_battmgr.c

@@ -1231,7 +1231,7 @@ static void qcom_battmgr_sc8280xp_strcpy(char *dest, const char *src)
 		memcpy(dest, src + 1, len);
 		dest[len] = '\0';
 	} else {
-		memcpy(dest, src, BATTMGR_STRING_LEN);
+		strscpy(dest, src, BATTMGR_STRING_LEN);
 	}
 }