efibc: EFI Bootloader control driver

efibc: EFI Bootloader control driver

Android userspace tells the kernel that it wants to boot into recovery
or some other non-default OS environment by passing a string argument
to reboot(). It is left to the OEM to hook this up to their specific
bootloader.

This driver uses an EFI variable to communicate the next boot target.

It is the bootloader's job to guard against this variable being
uninitialzed or containing invalid data, and just boot normally if that
is the case.

Signed-off-by: Matt Gumbel <matthew.k.gumbel@intel.com>
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>