staging: rtl8712: fix stack dump

staging: rtl8712: fix stack dump

del_timer_sync() is not to be called in the interrupt context unless
the timer is irqsafe. but most of the functions where commits
6501c8e7d86cca5f and 382d020f4459cd77 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: 382d020f4459cd77 ("Staging: rtl8712: Eliminate use of _cancel_timer"
Fixes: 6501c8e7d86cca5f ("Staging: rtl8712: Eliminate use of _cancel_timer_ex")
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=97711
Reported-by: Arek Rusniak <arek.rusi@gmail.com>
Tested-by: Arek Rusniak <arek.rusi@gmail.com>
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>