arch/x86/Kconfig: CONFIG_X86_UV should depend on CONFIG_EFI

arch/x86/built-in.o: In function `uv_bios_call':
(.text+0xeba00): undefined reference to `efi_call'

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>