rtc: ds3232: fix WARNING trace in resume function

If ds3232 work on some platform that is not implementing
irq_set_wake, ds3232 will get a WARNING trace in resume.
So fix ds3232->suspended state to false when irq_set_irq_wake
return error.

WARNING: CPU: 0 PID: 729 at kernel/irq/manage.c:604 irq_set_irq_wake+0x4b/0x8c()
Unbalanced IRQ 201 wake disable
Modules linked in:
CPU: 0 PID: 729 Comm: sh Not tainted 3.12.19-rt30+ #25
[<800107d9>] (unwind_backtrace+0x1/0x88) from [<8000e4ef>] (show_stack+0xb/0xc)
[<8000e4ef>] (show_stack+0xb/0xc) from [<802b5fa9>] (dump_stack+0x4d/0x60)
[<802b5fa9>] (dump_stack+0x4d/0x60) from [<800186dd>] (warn_slowpath_common+0x45/0x64)
[<800186dd>] (warn_slowpath_common+0x45/0x64) from [<80018717>] (warn_slowpath_fmt+0x1b/0x24)
[<80018717>] (warn_slowpath_fmt+0x1b/0x24) from [<8003a8d3>] (irq_set_irq_wake+0x4b/0x8c)
[<8003a8d3>] (irq_set_irq_wake+0x4b/0x8c) from [<80204fcb>] (ds3232_resume+0x2d/0x36)
[<80204fcb>] (ds3232_resume+0x2d/0x36) from [<801954c7>] (dpm_run_callback.isra.13+0xb/0x28)
[<801954c7>] (dpm_run_callback.isra.13+0xb/0x28) from [<80195b1b>] (device_resume+0x7b/0xa2)
[<80195b1b>] (device_resume+0x7b/0xa2) from [<80195f0f>] (dpm_resume+0xbb/0x19c)
[<80195f0f>] (dpm_resume+0xbb/0x19c) from [<801960d9>] (dpm_resume_end+0x9/0x12)
[<801960d9>] (dpm_resume_end+0x9/0x12) from [<80037e1d>] (suspend_devices_and_enter+0x17d/0x1d0)
[<80037e1d>] (suspend_devices_and_enter+0x17d/0x1d0) from [<80037ee1>] (pm_suspend+0x71/0x128)
[<80037ee1>] (pm_suspend+0x71/0x128) from [<80037449>] (state_store+0x6d/0x80)
[<80037449>] (state_store+0x6d/0x80) from [<800af4d5>] (sysfs_write_file+0x9f/0xde)
[<800af4d5>] (sysfs_write_file+0x9f/0xde) from [<8007a437>] (vfs_write+0x7b/0x104)
[<8007a437>] (vfs_write+0x7b/0x104) from [<8007a7f7>] (SyS_write+0x27/0x48)
[<8007a7f7>] (SyS_write+0x27/0x48) from [<8000c121>] (ret_fast_syscall+0x1/0x44)

Signed-off-by: Wang Dongsheng <dongsheng.wang@freescale.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>