del_timer_sync() is not to be called in the interrupt context unless
the timer is irqsafe. but most of the functions where commits
6501c8e7 and 382d020f touched were called in interrupt
context. And as a result the WARN_ON was getting triggered. Changed
to del_timer() in places which were called from interrupt.

Fixes: 382d020f ("Staging: rtl8712: Eliminate use of _cancel_timer"
Fixes: 6501c8e7 ("Staging: rtl8712: Eliminate use of _cancel_timer_ex")
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=97711Reported-by: NArek Rusniak <arek.rusi@gmail.com>
Tested-by: NArek Rusniak <arek.rusi@gmail.com>
Signed-off-by: NSudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>