fix omap_drv compilation
    
    drivers/staging/omapdrm/omap_drv.c:764:3: error: unknown field 'reclaim_buffers' specified in initializer
    drivers/staging/omapdrm/omap_drv.c:764:3: error: initialization from incompatible pointer type [-Werror]
    drivers/staging/omapdrm/omap_drv.c:764:3: error: (near initialization for 'omap_drm_driver.irq_preinstall') [-Werror]
    
    Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>