scsi: fcoe: Simplify if-if to if-else

scsi: fcoe: Simplify if-if to if-else

Replace 'if (!is_zero_ether_addr(mac))' with 'else' for simplification and
add curly brackets according to the kernel coding style:

"Do not unnecessarily use braces where a single statement will do."

...

"This does not apply if only one branch of a conditional statement is a
single statement; in the latter case use braces in both branches"

Please refer to:
https://www.kernel.org/doc/html/v5.17-rc8/process/coding-style.html

Link: https://lore.kernel.org/r/20220408081237.14037-1-hanyihao@vivo.com
Signed-off-by: Yihao Han <hanyihao@vivo.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>