iwlwifi: prepare for higher API/CAPA bits

Currently, loading the firmware fails when it has higher API or CAPA
bits than the driver supports. That's an issue with integration.

At the same time, actually using api[0] and capa[0] will become
confusing when we also have api[1] and capa[1], and it's almost
certain that we'll mix up the bits and use the bits for api[1] with
api[0] by accident.

Avoid all this by translating the API/CAPA bits to the regular kernel
test_bit() format, and also providing wrapper functions. Also use the
__bitwise__ facility of sparse to check that we're testing the right
one.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>