dmaengine: dmatest: Explicitly cast divisor to u32

As the comment explains, the while loop ensures that runtime fits into
32 bits. Since do_div() casts the divisor to u32 anyway, explicitly cast
runtime to u32 to remove the following Coccinelle/coccicheck warning
reported by do_div.cocci:

WARNING: do_div() does a 64-by-32 division, please consider using div64_s64 instead

Signed-off-by: Thorsten Blum <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/dmatest.c

···
 
 	per_sec *= val;
 	per_sec = INT_TO_FIXPT(per_sec);
-	do_div(per_sec, runtime);
+	do_div(per_sec, (u32)runtime);
 
 	return per_sec;
 }