efi: Enforce minimum alignment of 1 page on allocations.

The efi_high_alloc() and efi_low_alloc() functions
use the EFI_ALLOCATE_ADDRESS option to the EFI
function allocate_pages(), which requires a minimum
of page alignment, and rejects all other requests.
The existing code could fail to allocate depending
on allocation size, as although repeated allocation
attempts were made, none were guaranteed to be page
aligned.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Mark Salter <msalter@redhat.com>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>