libfdt: add fdt_get_property_by_offset_w helper

Add a new fdt_get_property_by_offset_w helper function.
It is a wrapper on fdt_get_property_by_offset that returns
a writable pointer to a property at a given offset.

Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Message-Id: <20221011182611.116011-1-tadeusz.struk@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/libfdt.h

@@ -660,6 +660,13 @@ int fdt_next_property_offset(const void *fdt, int offset);
 const struct fdt_property *fdt_get_property_by_offset(const void *fdt,
 						      int offset,
 						      int *lenp);
+static inline struct fdt_property *fdt_get_property_by_offset_w(void *fdt,
+								int offset,
+								int *lenp)
+{
+	return (struct fdt_property *)(uintptr_t)
+		fdt_get_property_by_offset(fdt, offset, lenp);
+}
 
 /**
  * fdt_get_property_namelen - find a property based on substring