rcu: Don't use modular infrastructure in non-modular code

The Kconfig currently controlling compilation of tree.c is:

init/Kconfig:config TREE_RCU
init/Kconfig:   bool

...and update.c and sync.c are "obj-y" meaning that none are ever
built as a module by anyone.

Since MODULE_ALIAS is a no-op for non-modular code, we can remove
them from these files.

We leave moduleparam.h behind since the files instantiate some boot
time configuration parameters with module_param() still.

Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>