modpost symbol prefix setting

modpost symbol prefix setting

[bwh: The original version of this was added by Bastian Blank.  The
upstream code includes <generated/autoconf.h> so that <linux/export.h>
can tell whether C symbols have an underscore prefix.  Since we build
modpost separately from the kernel, <generated/autoconf.h> won't exist.
However, no Debian Linux architecture uses the symbol prefix, so we
can simply omit it.]

Gbp-Pq: Topic debian
Gbp-Pq: Name modpost-symbol-prefix.patch