spi: spi-mem: Fix a memory leak in spi_mem_dirmap_destroy()

The dirmap descriptor object allocated in spi_mem_dirmap_create is
never freed. Add a kfree(desc) in spi_mem_dirmap_destroy().

Fixes: aa167f3fed ("spi: spi-mem: Add a new API to support direct mapping")
Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mem.c

@@ -547,6 +547,8 @@ void spi_mem_dirmap_destroy(struct spi_mem_dirmap_desc *desc)
 
 	if (!desc->nodirmap && ctlr->mem_ops && ctlr->mem_ops->dirmap_destroy)
 		ctlr->mem_ops->dirmap_destroy(desc);
+
+	kfree(desc);
 }
 EXPORT_SYMBOL_GPL(spi_mem_dirmap_destroy);