staging: rtl8723bs: remove redundant comparisons of unsigned ints with >= 0

The comparison of mode >= 0 is redundant as mode is a u32 and this
is always true.  Remove this redundant code.

Detected with CoverityScan ("Unsigned compared against 0")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>