drm/i915/bios: Parse HOBL parameter

HOBL means hours of battery life, it is a power-saving feature
were supported motherboards can use a special voltage swing table
that uses less power.

So here parsing the VBT to check if this feature is supported.

BSpec: 20150
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200708205512.21625-3-jose.souza@intel.com