lib: sbi: Introduce simple heap allocator

We provide simple heap allocator to manage the heap space provided
by OpenSBI firmware and platform.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

include/sbi/sbi_heap.h

@@ -0,0 +1,44 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 Ventana Micro Systems Inc.
+ *
+ * Authors:
+ *   Anup Patel<apatel@ventanamicro.com>
+ */
+
+#ifndef __SBI_HEAP_H__
+#define __SBI_HEAP_H__
+
+#include <sbi/sbi_types.h>
+
+struct sbi_scratch;
+
+/** Allocate from heap area */
+void *sbi_malloc(size_t size);
+
+/** Zero allocate from heap area */
+void *sbi_zalloc(size_t size);
+
+/** Allocate array from heap area */
+static inline void *sbi_calloc(size_t nitems, size_t size)
+{
+	return sbi_zalloc(nitems * size);
+}
+
+/** Free-up to heap area */
+void sbi_free(void *ptr);
+
+/** Amount (in bytes) of free space in the heap area */
+unsigned long sbi_heap_free_space(void);
+
+/** Amount (in bytes) of used space in the heap area */
+unsigned long sbi_heap_used_space(void);
+
+/** Amount (in bytes) of reserved space in the heap area */
+unsigned long sbi_heap_reserved_space(void);
+
+/** Initialize heap area */
+int sbi_heap_init(struct sbi_scratch *scratch);
+
+#endif