[media] media: ti-vpe: sc: Fix incorrect optimization

Current scaler library implementation of sc_set_hs_coeffs and
sc_set_vs_coeffs tries to return immediately if the calculated
coefficient index is already being used.

As the same scaler block is going to be used for all the VPE contexts,
even if the calculated index is same, the parameters have to be
reconfigured for each of the context.

Because of this, when multiple contexts use the same coefficients,
all other contexts would have zero scaling coefficients.
Fix this and also remove the unnecessary hs_index and vs_index fields.

Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>