clocksource/drivers/sh_tmu: Fix traceback spotted in -next

Traceback in -next due to commit 'clockevents/drivers/sh_tmu: Migrate to new
'set-state' interface'.

Commit ("clockevents/drivers/sh_tmu: Migrate to new 'set-state' interface")
in -next causes the following traceback. This is seen with qemu runs for the sh
target.

------------[ cut here ]------------
WARNING: at drivers/clocksource/sh_tmu.c:202
Modules linked in:

CPU: 0 PID: 0 Comm: swapper Not tainted 4.2.0-rc3-next-20150720 #1
task: 8c411ed8 ti: 8c40e000 task.ti: 8c40e000
PC is at sh_tmu_disable+0x40/0x60
PR is at sh_tmu_clock_event_shutdown+0x8/0x20
PC  : 8c271220 SP  : 8c40ff10 SR  : 400081f1 TEA : 00000000
R0  : 8c271240 R1  : 8fc08cfc R2  : 00000000 R3  : 3fffffff
R4  : 8fc08c00 R5  : 00000001 R6  : 00000002 R7  : ffffffff
R8  : 00000001 R9  : 8fc08c20 R10 : 00000000 R11 : 00000000
R12 : 8c012820 R13 : 00000000 R14 : 00000000
MACH: 3b9ac9ff MACL: 80000000 GBR : 00000000 PR  : 8c271248

Call trace:
 [<8c065836>] clockevents_switch_state+0x16/0x60
 [<8c06588c>] clockevents_shutdown+0xc/0x40
 [<8c066330>] tick_check_new_device+0x90/0xc0
 [<8c065556>] clockevents_register_device+0x56/0x120
 [<8c0662a0>] tick_check_new_device+0x0/0xc0
 [<8c27167a>] sh_tmu_probe+0x29a/0x4e0
 [<8c18a994>] kasprintf+0x14/0x20
 [<8c442782>] early_platform_driver_probe+0x20e/0x2bc
 [<8c1fade0>] platform_match+0x0/0x100
 [<8c33babc>] printk+0x0/0x24
 [<8c434892>] start_kernel+0x32e/0x574
 [<8c33babc>] printk+0x0/0x24
 [<8c17d320>] strlen+0x0/0x58
 [<8c43430c>] unknown_bootoption+0x0/0x1e0
 [<8c011024>] _stext+0x24/0x30

---[ end trace cb88537fdc8fa200 ]---

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>