Avoid unused output warning on some systems
Avoid unused output warning on some systems

lib/fw.c: In function switchtec_fw_read_fd:
lib/fw.c:599:3: warning: ignoring return value of write,
declared with attribute warn_unused_result [-Wunused-result]
   write(fd, buf, ret);

Microsemi/switchtec-user,Microsemi/switchtec-user