efi/arm*: esrt: Add missing call to efi_esrt_init()

ESRT support is built by default for all architectures that define
CONFIG_EFI. However, this support was not wired up yet for ARM/arm64,
since efi_esrt_init() was never called. So add the missing call.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Jones <pjones@redhat.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>