i40e: fix misleading indentation

Newly added code in i40e_vc_config_promiscuous_mode_msg() is indented
in a way that gcc rightly complains about:

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c: In function 'i40e_vc_config_promiscuous_mode_msg':
drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c:1543:4: error: this 'if' clause does not guard... [-Werror=misleading-indentation]
    if (f->vlan >= 0 && f->vlan <= I40E_MAX_VLANID)
    ^~
drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c:1550:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
     aq_err = pf->hw.aq.asq_last_status;

From the context, it looks like the aq_err assignment was meant to be
inside of the conditional expression, so I'm adding the appropriate
curly braces now.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 5676a8b9 ("i40e: Add VF promiscuous mode driver support")
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>