iwlwifi: mvm: force single phy init

The PHY is initialized during device initialization, but devices with
the tx_siso_diversity flag set need to send PHY_CONFIGURATION_CMD first,
otherwise the PHY would be reinitialized, causing a SYSASSERT.

To fix this, use a bit that tells the FW not to complete the PHY
initialization before a PHY_CONFIGURATION_CMD is received.

Signed-off-by: Haim Dreyfuss <haim.dreyfuss@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>