freedreno: Handle DRM_FORMAT_MOD_INVALID in shared code
layout_resource_for_modifier() needs to handle DRM_FORMAT_MOD_INVALID as well, since src/gallium/frontends/dri/dri2.c uses this to indicate "no modifier" when it's called through the older non-modifier entry points.
This is similar to 334788d4 ("freedreno: allow INVALID modifier") but for the generic implementation.
Fixes: 98910626 ("freedreno/a6xx: Implement layout for DRM_FORMAT_MOD_QCOM_COMPRESSED")