Staging: wilc1000: Remove unused function WILC_WFI_update_stats

This patch removes the function WILC_WFI_update_stats as it is not used
anywhere in the kernel. Also remove its declaration from the header
file. Grepped to find the occurences.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>