efi: Remove unnecessary (and buggy) .memmap initialization from the Xen EFI driver

So the following commit:

  884f4f66ff ("efi: Remove global 'memmap' EFI memory map")

... triggered the following build warning on x86 64-bit allyesconfig:

drivers/xen/efi.c:290:47: warning: missing braces around initializer [-Wmissing-braces]

It's this initialization in drivers/xen/efi.c:

  static const struct efi efi_xen __initconst = {
  ...
        .memmap                   = NULL, /* Not used under Xen. */
  ...

which was forgotten about, as .memmap now is an embedded struct:

        struct efi_memory_map memmap;

We can remove this initialization - it's an EFI core internal data structure plus
it's not used in the Xen driver anyway.

Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: ard.biesheuvel@linaro.org
Cc: bp@alien8.de
Cc: linux-tip-commits@vger.kernel.org
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/20160429083128.GA4925@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/xen/efi.c

@@ -316,7 +316,6 @@ static const struct efi efi_xen __initconst = {
 	.get_next_high_mono_count = xen_efi_get_next_high_mono_count,
 	.reset_system             = NULL, /* Functionality provided by Xen. */
 	.set_virtual_address_map  = NULL, /* Not used under Xen. */
-	.memmap                   = NULL, /* Not used under Xen. */
 	.flags			  = 0     /* Initialized later. */
 };