m32r: Use generic PREEMPT config

Use the generic preempt config definition in m32r instead of
using a custom one.

This also makes it handle the new CONFIG_PREEMPT_COUNT that
need to be selected by CONFIG_PREEMPT.

Without that it breaks

  kernel/sched.c: In function 'preempt_schedule':
  kernel/sched.c:4364: error: implicit declaration of function 'add_preempt_count_notrace'
  kernel/sched.c:4366: error: implicit declaration of function 'sub_preempt_count_notrace'
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>

arch/m32r/Kconfig

@@ -268,17 +268,7 @@ config SCHED_OMIT_FRAME_POINTER
         bool
         default y
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	help
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-	  This allows applications to run more reliably even when the system is
-	  under load.
-
-	  Say Y here if you are building a kernel for a desktop, embedded
-	  or real-time system.  Say N if you are unsure.
+source "kernel/Kconfig.preempt"
 
 config SMP
 	bool "Symmetric multi-processing support"