OMAPDSS: DISPC: Use FIR filters other than M19

Pass correct arguments to FIR filter selection.  Previously we
always ended up selecting M19 5-tap filter.

This should improve image quality of scaled layers.

Change-Id: Iabe3219df7dcfd62c713fd92ee9c3d12221bc382
Signed-off-by: Lajos Molnar <lajos@ti.com>