ice: Fix VFR issues for AVF drivers that expect ATQLEN cleared

Some AVF drivers expect the VF_MBX_ATQLEN register to be cleared for any
type of VFR/VFLR. Fix this by clearing the VF_MBX_ATQLEN register at the
same time as VF_MBX_ARQLEN.

Fixes: 82ba0128

 ("ice: clear VF ARQLEN register on reset")
Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>