platform/x86: dell-wmi-sysman: work around for BIOS bug

BIOS sets incorrect value (zero) when SET value passed for integer
attribute with + sign. Added workaround to remove + sign before passing
input to BIOS.

Co-developed-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Co-developed-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Divya Bharathi <divya.bharathi@dell.com>
Link: https://lore.kernel.org/r/20201202131935.307372-1-divya.bharathi@dell.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>