wifi: iwlwifi: mvm: fold the ref++ into iwl_mvm_phy_ctxt_add

When we want to add a phy_ctxt, we need to increase the ref.
Note that all the WARN_ONs are already in place:
* We check that we don't add a context with ref != 0
* We check that we don't modify a context with ref = 0

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20231011130030.c19c07746b26.I5b0cbe0760811631a320218a10b88870b5bf0897@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>