gcc trunk fails to build kernel on PowerPC64 due to oprofile warnings

[David Laight]

From: Anton Blanchard
> Sent: 25 January 2017 23:01
> gcc trunk has failed to build PowerPC64 kernels for a month or so. The issue
> is in oprofile, which is common code but ends up being sucked into
> arch/powerpc and therefore subject to the -Werror applied to arch/powerpc:
...
> linux/arch/powerpc/oprofile/../../../drivers/oprofile/oprofile_stats.c:55:25: error: %d directive
> output may be truncated writing between 1 and 11 bytes into a region of size 7 [-Werror=format-
> truncation=]
>    snprintf(buf, 10, "cpu%d", i);

FFS these warnings are getting OTT.
The compiler needs to be able to track the domain of integers before applying
some of these warnings.

	David