loader: remove clamp_swap_interval()

loader: remove clamp_swap_interval()

As of last commit, no invalid swap interval can be stored, so there's
no need to sanitize the values when reading them anymore.

Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>