[media] staging: atomisp: Fix calling efivar_entry_get() with unaligned arguments

efivar_entry_get has certain alignment requirements and the atomisp
platform code was not honoring these, causing an oops by triggering the
WARN_ON in arch/x86/platform/efi/efi_64.c: virt_to_phys_or_null_size().

This commit fixes this by using the members of the efivar struct embedded
in the efivar_entry struct we kzalloc as arguments to efivar_entry_get(),
which is how all the other callers of efivar_entry_get() do this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>