Fix an uninitialized variable as well as an stdarg cleanup. (CID: 1194318 and 1194332)

[araujo]

Summary

CID 1194318: We call the macro EFPRINTF without initialize the variable err.
CID 1194332: stdarg(3) says that each invocation of va_start() must be paired with a corresponding invocation of va_end() in the same function. In this case if an error occur with vfprintf() we forget to call va_end(ap).

Test Plan

Tested with FreeeBSD HEAD as a vm guest.
Tested with Fedora as a vm guest.

[jhb]

So I looked at acpi.c and I have a couple of thoughts:

1. style(9) discourages assignments in declarations and the rest of acpi.c follows that by setting err to 0 on separate lines

2. But bigger than that, the whole 'err' variable isn't necessary. EFPRINTF should just be:

if (fprintf(__VA_ARGS__) < 0) goto err_exit;

Likewise, EFFLUSH should check the return value of fflush() directly. The spurious 'err' variables should then be removed.

[araujo]

Simplify both macros EFPRINTF and EFFLUSH and remove the unnecessary variable 'err'.
Likewise, remove varible 'err' from some functions that uses those two macros.

Thanks @jhb!