drm/i915/intel_fb: Factor out calc_plane_remap_info()

Factor out to a new function the logic to calculate the FB remapping
parameters both during creating the FB and when flipping to it.

v2:
- Keep stride next to offset calculation. (Ville)
- Enclose check_array_bounds macro arguments in parentheses.
v3:
- Rebase on top of the struct intel_fb_view refactoring.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210325214808.2071517-20-imre.deak@intel.com