dts: sram: Simplify the description of the binding

Remove redundant descriptions in SRAM bindings, such
as "... description".

Signed-off-by: James Roy <rruuaanng@outlook.com>

dts/bindings/sram/mmio-sram.yaml

@@ -1,7 +1,7 @@
 # Copyright (c) 2018, Linaro Limited
 # SPDX-License-Identifier: Apache-2.0
 
-description: Generic on-chip SRAM description
+description: Generic on-chip SRAM
 
 compatible: "mmio-sram"