uniphier: change the return value type of .is_usb_boot() to bool

This is boolean logic, so "bool" is more suitable.

Change-Id: I439c5099770600a65b8f58390a4c621c2ee487a5
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

plat/socionext/uniphier/uniphier_boot_device.c

 /*
- * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,17 +16,17 @@
 #define UNIPHIER_PINMON0		0x5f900100
 #define UNIPHIER_PINMON2		0x5f900108
 
-static int uniphier_ld11_is_usb_boot(uint32_t pinmon)
+static bool uniphier_ld11_is_usb_boot(uint32_t pinmon)
 {
 	return !!(~pinmon & 0x00000080);
 }
 
-static int uniphier_ld20_is_usb_boot(uint32_t pinmon)
+static bool uniphier_ld20_is_usb_boot(uint32_t pinmon)
 {
 	return !!(~pinmon & 0x00000780);
 }
 
-static int uniphier_pxs3_is_usb_boot(uint32_t pinmon)
+static bool uniphier_pxs3_is_usb_boot(uint32_t pinmon)
 {
 	uint32_t pinmon2 = mmio_read_32(UNIPHIER_PINMON2);
 
@@ -106,7 +106,7 @@ static unsigned int uniphier_pxs3_get_boot_device(uint32_t pinmon)
 }
 
 struct uniphier_boot_device_info {
-	int (*is_usb_boot)(uint32_t pinmon);
+	bool (*is_usb_boot)(uint32_t pinmon);
 	unsigned int (*get_boot_device)(uint32_t pinmon);
 };