x86: Work around compilation warning in arch/x86/kernel/apm_32.c

The following fix was initially inspired by David Howells fix
few days back:

  http://lkml.org/lkml/2009/7/9/109

However, Ingo disapproves such fixes as it's dangerous (it can
hide future, relevant warnings) - in something as
performance-uncritical.

So, initialize 'err' to '0' to work around a GCC false positive
warning:

  http://lkml.org/lkml/2009/7/18/89



Signed-off-by: Subrata <Modak&lt;subrata@linux.vnet.ibm.com>
Cc: Sachin P Sant <sachinp@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
LKML-Reference: <20090721023226.31855.67236.sendpatchset@subratamodak.linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>