OMAP: DSS2: FEATURES: Functions to return min and max values of parameters

Create 2 functions dss_feat_get_param_min() and dss_feat_get_param_max() which
return the minimum and maximum value of a parameter. Introduce a enum in
dss_features called dss_range_param which contains parameters whose ranges we
are interested in.

Replace this with dss_feat_get_max_dss_fck() which is specific to the parameter
DSS_FCK.

Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>