xdr: remove dead code, whitespace from xdr_enum

xdr: remove dead code, whitespace from xdr_enum

The 'enum sizecheck' declaration has been unused since openafs-ibm-1_0; it is
apparently vestigial from the original XDR code.  Remove it, along with some
extraneous whitespace.

No functional change is incurred by this commit.

Reviewed-on: https://gerrit.openafs.org/13076
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit fdc8adbf0904cbbc0590379c5cb702a15273b40c)

Change-Id: Ie586f210d17169a03143d1bdebb8430e3881e58c
Reviewed-on: https://gerrit.openafs.org/13184
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Joe Gorse <jhgorse@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>