hwmon: (asus_atk0110) Check package count before accessing element

atk_ec_present() walks the management group package returned by the GGRP
ACPI method and, for each sub-package, reads its first element:

	id = &obj->package.elements[0];
	if (id->type != ACPI_TYPE_INTEGER)

without checking that the sub-package is non-empty.  ACPICA allocates the
element array with exactly package.count entries, so for a sub-package
with a zero count this reads past the allocation.

The sibling function atk_debugfs_ggrp_open() performs the same access but
skips empty packages with a package.count check first.  Add the same
check to atk_ec_present() so a malformed firmware package cannot trigger
an out-of-bounds read.

Fixes: 9e6eba610c ("hwmon: (asus_atk0110) Enable the EC")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Link: https://lore.kernel.org/r/20260619122746.721981-1-sammiee5311@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/asus_atk0110.c

@@ -1037,6 +1037,9 @@ static int atk_ec_present(struct atk_data *data)
 		if (obj->type != ACPI_TYPE_PACKAGE)
 			continue;
 
+		if (!obj->package.count)
+			continue;
+
 		id = &obj->package.elements[0];
 		if (id->type != ACPI_TYPE_INTEGER)
 			continue;