[iscsictl] Fix compiler issues on gcc-6.4

[adrian]

Summary

This fixes two compiler warnings-that-are-errors:

• don't compare a uint64_t to be >= 0; it will always be that
• don't double-define yylex(); the definition for it is provided in a library header file.

[adrian]

hi! please lemme know what you think!

[imp]

usr.bin/iscsictl/parse.y

362 ↗

(On Diff #79025)

That doesn't look right at all now. What is it testing?

[adrian]

whoops brb

[adrian]

Fix!

[rscheff]

Looks good;