staging: wilc1000: remove redundant masking of pkt_offset

The masking update of pkg_offset is redundant as the updated
value is never read and pkg_offset is re-assigned on the next
iteration of the loop.  Clean this up by removing the redundant
assignment.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Adham Abozaeid <adham.abozaeid@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>