drm/nouveau/mmu/gp100-: drop unneeded assignment in the if condition.

In order to keep the code style consistency of the whole file,
the 'inst' assignments should be deleted.

The clang_analyzer complains as follows:

drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c:499:8: warning:
Although the value storedto 'inst' is used in the enclosing expression,
the value is never actually read from 'inst'.

Karol: Removed unneeded brackets.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Luo penghao <luo.penghao@zte.com.cn>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210821021447.27097-1-luo.penghao@zte.com.cn

drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c

@@ -502,7 +502,7 @@ gp100_vmm_fault_cancel(struct nvkm_vmm *vmm, void *argv, u32 argc)
 	args->v0.inst |= 0x80000000;
 
 	if (!WARN_ON(nvkm_gr_ctxsw_pause(device))) {
-		if ((inst = nvkm_gr_ctxsw_inst(device)) == args->v0.inst) {
+		if (nvkm_gr_ctxsw_inst(device) == args->v0.inst) {
 			gf100_vmm_invalidate(vmm, 0x0000001b
 					     /* CANCEL_TARGETED. */ |
 					     (args->v0.hub    << 20) |