iris: Fix assertion meant to only target the clear-color stride
Fixes: 2bc8c61f ("iris: Return a 64B stride for clear color plane") Closes: #6398 Signed-off-by:Jordan Justen <jordan.l.justen@intel.com> Reviewed-by:
Nanley Chery <nanley.g.chery@intel.com> Part-of: <!16241>