staging: rtl8188eu: Removed a function and coded inline

This patch removed function named rtw_malloc2d.

I removed this function because this function is used exactly once and
function call have some overhead also.

Maybe this will improve code runtime slightly.

Signed-off-by: Bhaskar Singh <bhaskar.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>