ice: Fix VSIs unable to share unicast MAC

The driver currently does not allow two VSIs in the same PF domain
to have the same unicast MAC address. This is incorrect in the sense
that a policy decision is being made in the driver when it must be
left to the user. This approach was causing issues when rebooting
the system with VFs spawned not being able to change their MAC addresses.
Such errors were present in dmesg:

[ 7921.068237] ice 0000:b6:00.2 ens2f2: Unicast MAC 6a:0d:e4:70:ca:d1 already
exists on this PF. Preventing setting VF 7 unicast MAC address to 6a:0d:e4:70:ca:d1

Fix that by removing this restriction. Doing this also allows
us to remove some additional code that's checking if a unicast MAC
filter already exists.

Fixes: 47ebc7b0

 ("ice: Check if unicast MAC exists before setting VF MAC")
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Signed-off-by: Sylwester Dziedziuch <sylwesterx.dziedziuch@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Signed-off-by: Jedrzej Jagielski <jedrzej.jagielski@intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>