gpu: host1x: fix an integer overflow check

Tegra is a 32 bit arch.  On 32 bit systems then size_t is 32 bits so
"total" will never be higher than UINT_MAX because of integer overflows.
We need cast to u64 first before doing the math.

Also the addition earlier:

        unsigned int num_unpins = num_cmdbufs + num_relocs;

That can overflow as well, but I think it's still safe because we check
both "num_cmdbufs" and "num_relocs" again in this test.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/host1x/job.c

@@ -42,12 +42,12 @@ struct host1x_job *host1x_job_alloc(struct host1x_channel *ch,
 
 	/* Check that we're not going to overflow */
 	total = sizeof(struct host1x_job) +
-		num_relocs * sizeof(struct host1x_reloc) +
-		num_unpins * sizeof(struct host1x_job_unpin_data) +
-		num_waitchks * sizeof(struct host1x_waitchk) +
-		num_cmdbufs * sizeof(struct host1x_job_gather) +
-		num_unpins * sizeof(dma_addr_t) +
-		num_unpins * sizeof(u32 *);
+		(u64)num_relocs * sizeof(struct host1x_reloc) +
+		(u64)num_unpins * sizeof(struct host1x_job_unpin_data) +
+		(u64)num_waitchks * sizeof(struct host1x_waitchk) +
+		(u64)num_cmdbufs * sizeof(struct host1x_job_gather) +
+		(u64)num_unpins * sizeof(dma_addr_t) +
+		(u64)num_unpins * sizeof(u32 *);
 	if (total > ULONG_MAX)
 		return NULL;