[media] rc-main: store_filter: pass errors to userland

Propagate errors returned by drivers from the s_filter callback back to
userland when updating scancode filters. This allows userland to see
when the filter couldn't be updated, usually because it's not a valid
filter for the hardware.

Previously the filter was being updated conditionally on success of
s_filter, but the write always reported success back to userland.

Reported-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>