ARM: multi_v7_defconfig: enable CONFIG_EFI

This enables CONFIG_EFI for multi_v7_defconfig, which adds support for
booting via EFI, and for the EFI framebuffer as builtin options. It
also enables the EFI rtc, the EFI variable pseudo-filesystem and the
EFI capsule loader as modules.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>