mwifiex: correction in structure name passed to sizeof()

"hscfg" is declared as struct mwifiex_ds_hs_cfg. Use same structure
name for calculating it's size.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>