x86/efi: Delete SGI UV1 detection.

As a part of UV1 platform removal, don't try to recognize the platform
through DMI to set the EFI_UV1_MEMMAP bit.

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lkml.kernel.org/r/20200713212955.667726896@hpe.com