mwifiex: fix wrong data rates in P2P client

This patch fixes an issue wherein adhoc rates were being copied
into association request from P2P client.

Cc: <stable@vger.kernel.org> # 3.10.y
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Stone Piao <piaoyun@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>