ACPICA: Utilities: Fix local printf issue.

The bug can be reproduced by using a format that do not have the width.prec
specified after a format that have the width.prec specified. The second
formatted output will be wrong. The root cause is acpi_ut_vsnprintf()
doesn't reset the specifiers to the default values.

This patch fixes this issue. BZ 1094. Reported by Yizhe Wang, fixed by
Lv Zheng.

Since acpi_ut_vprintf() is only enabled for specific OSPM now, this patch
doesn't affect Linux kernel.

Link: https://bugs.acpica.org/show_bug.cgi?id=1094
Reported-and-tested-by: Yizhe Wang <yizhe.wang@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>