Invariant result in opts-visitor.c
Description of problem:
Expressions:
1) val2 <= INT64_MAX
2) INT64_MIN <= val2
in line [431](https://github.com/qemu/qemu/blob/62dbe54c24dbf77051bafe1039c31ddc8f37602d/qapi/opts-visitor.c#L431) are always true.

Seems like this checks are redundant.

Found by Linux Verification Center (portal.linuxtesting.ru) with SVACE.

Author A. Burke.