UKERNEL: End the #define u insanity

UKERNEL: End the #define u insanity

UKERNEL redefines the character 'u' to do a function call. This
hurts other kernel developers in all sorts of interesting ways. Remove
the definition, and instead explicitly reference the get_user_struct()
function in those places that we need to.

Change-Id: I64be2eb527c779df0a3d4508444ed68f3634667d
Reviewed-on: http://gerrit.openafs.org/1243
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>