cfg80211: Validate cipher suite against supported ciphers

Instead of using a hardcoded list of cipher suites in nl80211.c, use a
shared function in util.c to verify that the driver advertises support
for the specified cipher. This provides more accurate validation of the
values and allows vendor-specific cipher suites to be added in drivers.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>