Revert "LOCAL / drm/exynos: fimd: Remove unused 'ret' variable"

Revert "LOCAL / drm/exynos: fimd: Remove unused 'ret' variable"

This reverts commit aacf1c3ffc5a1a1ba1d51e258b4af722d68c6407 to fix
build error (tizen_trats2_defconfig):
../drivers/gpu/drm/exynos/exynos_drm_fimd.c: In function ‘fimd_bind’:
../drivers/gpu/drm/exynos/exynos_drm_fimd.c:1037:3: error: ‘ret’ undeclared (first use in this function)
../drivers/gpu/drm/exynos/exynos_drm_fimd.c:1037:3: note: each undeclared identifier is reported only once for each function it appears in
make[5]: *** [drivers/gpu/drm/exynos/exynos_drm_fimd.o] Error 1