usb: early: convert to readl_poll_timeout_atomic()

Use readl_poll_timeout_atomic() to simplify code

Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1600668815-12135-1-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/early/xhci-dbc.c

@@ -14,6 +14,7 @@
 #include <linux/pci_ids.h>
 #include <linux/memblock.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <asm/pci-direct.h>
 #include <asm/fixmap.h>
 #include <linux/bcd.h>
@@ -135,16 +136,9 @@ static int handshake(void __iomem *ptr, u32 mask, u32 done, int wait, int delay)
 {
 	u32 result;
 
-	do {
-		result = readl(ptr);
-		result &= mask;
-		if (result == done)
-			return 0;
-		udelay(delay);
-		wait -= delay;
-	} while (wait > 0);
-
-	return -ETIMEDOUT;
+	return readl_poll_timeout_atomic(ptr, result,
+					 ((result & mask) == done),
+					 delay, wait);
 }
 
 static void __init xdbc_bios_handoff(void)