Introduce new fdt helper to read string properties

Introduced fdtw_read_string() to read string properties.

Change-Id: I854eef0390632cf2eaddd2dce60cdb98c117de43
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/common/fdt_wrappers.h b/include/common/fdt_wrappers.h
index 3eae944..a0fe6b7 100644
--- a/include/common/fdt_wrappers.h
+++ b/include/common/fdt_wrappers.h
@@ -14,6 +14,9 @@
 
 int fdtw_read_cells(const void *dtb, int node, const char *prop,
 		unsigned int cells, void *value);
+int fdtw_read_string(const void *dtb, int node, const char *prop,
+		char *str, size_t size);
 int fdtw_write_inplace_cells(void *dtb, int node, const char *prop,
 		unsigned int cells, void *value);
+
 #endif /* __FDT_WRAPPERS__ */