LINUX: Reduce stack depth on recursive symlink res

LINUX: Reduce stack depth on recursive symlink res

Instead of calling vfs_follow_link inside afs_linux_follow_link
ourselves, we can just resolve the next step of the symlink resolution
and set the result in nd_set_link(), freeing the string in
.put_link().

For kernels without a usable symlink text cache, this reduces call
depth when resolving a path containing many symlinks by two frames per
layer of indirection, allowing for more deeply-nested symlink paths to
be usable.

Reviewed-on: http://gerrit.openafs.org/3433
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 2ce159fbf474b96ecd2a4224751d4655230bba51)

Change-Id: Idb91c2bb1a10b60d125dccbc98731ace63d4add8
Reviewed-on: http://gerrit.openafs.org/6269
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>