NFS: Fix the fix to Bugzilla #11061, when IPv6 isn't defined...

Stephen Rothwell reports:

Today's linux-next build (powerpc ppc64_defconfig) failed like this:

fs/built-in.o: In function `.nfs_get_client':
client.c:(.text+0x115010): undefined reference to `.__ipv6_addr_type'

Fix by moving the IPV6 specific parts of commit
d7371c41 ("Bug 11061, NFS mounts dropped")
into the '#ifdef IPV6..." section.

Also fix up a couple of formatting issues.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>