An OEM may request increased I_boost beyond the recommended values
by specifying an I_boost value to be applied to all swing entries for
a port. These override values are specified in VBT.

v2: rebase and remove unused iboost_bit variable

Issue: VIZ-5676
Signed-off-by: NAntti Koskipaa <antti.koskipaa@linux.intel.com>
Reviewed-by: NDavid Weinehall <david.weinehall@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>