thermal: rcar_thermal: Prevent doing work after unbind

thermal: rcar_thermal: Prevent doing work after unbind

When testing bind/unbind on r8a7791/koelsch:

    WARNING: CPU: 1 PID: 697 at lib/debugobjects.c:329 debug_print_object+0x8c/0xb4
    ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x10

This happens if the workqueue runs after the device has been unbound.
Fix this by cancelling any queued work during remove.

Fixes: e0a5172e9eec7f0d ("thermal: rcar: add interrupt support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>