phy: cpcap-usb: Simplify bool conversion

Fix the following coccicheck warning:
./drivers/phy/motorola/phy-cpcap-usb.c:146:31-36: WARNING: conversion to
bool not needed here
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1611905915-50394-1-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/motorola/phy-cpcap-usb.c

@@ -143,7 +143,7 @@ static bool cpcap_usb_vbus_valid(struct cpcap_phy_ddata *ddata)
 
 	error = iio_read_channel_processed(ddata->vbus, &value);
 	if (error >= 0)
-		return value > 3900 ? true : false;
+		return value > 3900;
 
 	dev_err(ddata->dev, "error reading VBUS: %i\n", error);