mwifiex: keep original structure in decl header file

memory_type_mapping strucuture did not refer to other mwifiex
specific strture. A better software design method would keep
it in decl header file, which does not include other mwifiex
header file.

Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>