staging: wilc1000: Remove unnecessary extern variables.

Extern variables and functions used in only one file were removed
from .h files, and made static in the .c files they're used.

Extern variable wilc_initialized was declared and never used, so it was
removed.

Signed-off-by: Elise Lennion <elise.lennion@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>