efi/libstub/arm64: align PE/COFF sections to segment alignment

efi/libstub/arm64: align PE/COFF sections to segment alignment

The arm64 kernel's segment alignment is fixed at 64 KB for any page
size, and relocatable kernels are able to fix up any misalignment of
the kernel image with respect to the 2 MB section alignment that is
mandated by the arm64 boot protocol.

Let's increase the PE/COFF section alignment to the same value, so that
kernels loaded by the UEFI PE/COFF loader are guaranteed to end up at
an address that doesn't require any reallocation to be done if the
kernel is relocatable.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20200413155521.24698-6-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>