x86/platform/UV: Use efi_enabled() instead of test_bit()

Use ad hoc efi_enabled() instead of fiddling with test_bit().

Cleanup, no functional changes.

Signed-off-by: Hedi Berriche <hedi.berriche@hpe.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Russ Anderson <rja@hpe.com>
Reviewed-by: Dimitri Sivanich <sivanich@hpe.com>
Reviewed-by: Mike Travis <mike.travis@hpe.com>
Cc: Andy Shevchenko <andy@infradead.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: platform-driver-x86@vger.kernel.org
Cc: Steve Wahl <steve.wahl@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190213193413.25560-4-hedi.berriche@hpe.com