rtlwifi: rtl8192de: Fix missing enable interrupt flag

commit 330bb711 upstream.

In commit 38506ece ("rtlwifi: rtl_pci: Start modification for
new drivers"), the flag that indicates that interrupts are enabled was
never set.

In addition, there are several places when enable/disable interrupts
were commented out are restored. A sychronize_interrupts() call is
removed.

Fixes: 38506ece ("rtlwifi: rtl_pci: Start modification for new drivers")
Cc: Stable <stable@vger.kernel.org>	# v3.18+
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>