platform: Move platform common to lib/utils.

Currently, platform/common contains platform/non-platform specific
common minimal drivers and libraries. This is helpful is all platforms
are built within opensbi framework.

Move them to lib/utils so that any external platform code also can
reuse the minimalistic drivers or other common libraries.

This patch doesn't introduce any functional changes.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Acked-by: Anup Patel <anup.patel@wdc.com>

include/sbi_utils/irqchip/plic.h

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#ifndef __IRQCHIP_PLIC_H__
+#define __IRQCHIP_PLIC_H__
+
+#include <sbi/sbi_types.h>
+
+void plic_fdt_fixup(void *fdt, const char *compat);
+
+int plic_warm_irqchip_init(u32 target_hart, int m_cntx_id, int s_cntx_id);
+
+int plic_cold_irqchip_init(unsigned long base, u32 num_sources, u32 hart_count);
+
+#endif