drm/exec: use unique instead of local label

GCC forbids to jump to labels in loop conditions and a new clang
check stumbled over this.

So instead using a local label inside the loop condition use an
unique label outside of it.

Fixes: 09593216 ("drm: execution context for GEM buffers v7")
Link: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
Link: https://github.com/ClangBuiltLinux/linux/issues/1890
Link: https://github.com/llvm/llvm-project/commit/20219106060208f0c2f5d096eb3aed7b712f5067


Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
CC: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230731123625.3766-1-christian.koenig@amd.com