sfc: fix boolreturn.cocci warning and rename function

check_fcs() was returning bool as 0/1, which was a sign that the sense
 of the function was unclear: false was good, which doesn't really match
 a name like 'check_$thing'.  So rename it to ef100_has_fcs_error(), and
 use proper booleans in the return statements.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>