gpiolib: acpi: Prevent out-of-bounds pin access in OperationRegion handler

gpiolib: acpi: Prevent out-of-bounds pin access in OperationRegion handler

The ACPI GPIO OperationRegion handler receives pin offsets as a
64-bit address. Previously, this value could be assigned to a pin index
without validation, potentially causing out-of-bounds access if
the ACPI table provides an invalid offset.

This patch explicitly checks that the 64-bit address is less than
agpio->pin_table_length before using it, returning AE_BAD_PARAMETER
if the check fails. Additionally, it makes the length calculation
overflow-safe and ensures proper unsigned types for loop counters.

This corrects the commit message from v5 to accurately reflect the
underlying issue, removing references to truncation or wrap-around,
which do not occur in ACPICA.

Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Marco Scardovi <scardracs@disroot.org>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://patch.msgid.link/20260610154204.110379-3-scardracs@disroot.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>