staging: wilc1000: Remove unused function

Remove wilc_wlan_global_reset function since it is not used anywhere
in this driver.

This also silences the following sparse warning:
drivers/staging/wilc1000/wilc_wlan.c:1120:6: warning: symbol
'wilc_wlan_global_reset' was not declared. Should it be static?

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>