kmsdrm: Fix wrong check on KMSDRM_CreateWindow. A previous cleanup commit inverted a statement that checked the return value of a KMSDRM_CreateSurfaces call during KMSDRM_CreateWindow, which causes the video backend to always fail despite success. This commit restores the intended behavior. Fixes: 3c501b963dd8 ("Clang-Tidy fixes (#6725)"). (cherry picked from commit 0187209f461b84d22fc49a03369506e06448f47f)