rtc: Disable EFI rtc for x86

commit da167ad7 ("rtc: ia64: allow other architectures to use EFI
RTC") inadvertently introduced a regression for x86 because we've been
careful not to enable the EFI rtc driver due to the generally buggy
implementations of the time-related EFI runtime services.

In fact, since the above commit was merged we've seen reports of crashes
on 32-bit tablets,

  https://bugzilla.kernel.org/show_bug.cgi?id=84241#c21

Disable it explicitly for x86 so that we don't give users false hope
that this driver will work - it won't, and your machine is likely to
crash.
Acked-by: NMark Salter <msalter@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: <stable@vger.kernel.org> # v3.17
Signed-off-by: NMatt Fleming <matt.fleming@intel.com>

drivers/rtc/Kconfig

@@ -806,7 +806,7 @@ config RTC_DRV_DA9063
 
 config RTC_DRV_EFI
 	tristate "EFI RTC"
-	depends on EFI
+	depends on EFI && !X86
 	help
 	  If you say yes here you will get support for the EFI
 	  Real Time Clock.