net/smc: rename some 'fce' to 'fce_v2x' for clarity

Rename some functions or variables with 'fce' in their name but used in
SMCv2.1 as 'fce_v2x' for clarity.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>