powerpc/5xx: Drop unnecessary cast

do_div() does a 64-by-32 division, the 2nd parameter is a u32.

gbp->ipb_freq is already a u32, there's no need to transform it to u64
before passing it to do_div().
Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Add some detail to change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1644395696-3545-1-git-send-email-wangqing@vivo.com

arch/powerpc/platforms/52xx/mpc52xx_gpt.c

@@ -502,7 +502,7 @@ u64 mpc52xx_gpt_timer_period(struct mpc52xx_gpt_priv *gpt)
 	if (prescale == 0)
 		prescale = 0x10000;
 	period = period * prescale * 1000000000ULL;
-	do_div(period, (u64)gpt->ipb_freq);
+	do_div(period, gpt->ipb_freq);
 	return period;
 }
 EXPORT_SYMBOL(mpc52xx_gpt_timer_period);