generic: fix unrecognized opcode wsbh when building for MIPS16.

generic: fix unrecognized opcode wsbh when building for MIPS16.

The issue was found and reported by hynman [1] when compiling reaver for ar71xx
(Big Endian MIPS).

    {standard input}: Assembler messages:
    {standard input}:79: Error: unrecognized opcode `wsbh $2,$2'
    {standard input}:90: Error: unrecognized opcode `wsbh $3,$17'
    {standard input}:208: Error: unrecognized opcode `wsbh $2,$2'
    make[3]: *** [builder.o] Error 1

The patch was already in upstream since kernel release 4.3-rc5.

 [1] https://github.com/openwrt/packages/commit/1e29676a8ac74f797f8ca799364681cec575ae6f#commitcomment-12901931

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47322 3c298f89-4303-0410-b956-a3cf2f4a3e73