cache bypass: fix afs_bypass_copy_page memcpy oops

cache bypass: fix afs_bypass_copy_page memcpy oops

The two memory copy cases were inverted when the code was
refactored, causing an oops when cache bypass is enabled.

Change-Id: I30a9a51b7280883fb9b7bbeebbabe464c139b714
Reviewed-on: http://gerrit.openafs.org/8617
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>