mwifiex: correct packet length for packets from SDIO interface

commit d03b4aa77e1187b77dfe37d14a923547f00baa66 upstream.

While receiving a packet on SDIO interface, we allocate skb with
size multiple of SDIO block size. We need to resize this skb
after RX using packet length from RX header.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>