efi_loader: Fix section alignment on EFI binaries

efi_loader: Fix section alignment on EFI binaries

When creating EFI binaries, the alignment of the text section isn't
correctly factored in. As a result trying to load signed EFI binaries
throws an error with:

efi_image_region_add() efi_image_region_add: new region already part of another
Image not authenticated

Running the binary through sbverify has a similar warning
sbverify ./lib/efi_loader/helloworld.efi
warning: gap in section table:
    .text   : 0x00001000 - 0x00001c00,
    .data   : 0x00002000 - 0x00002200,
gaps in the section table may result in different checksums
warning: data remaining[7680 vs 12720]: gaps between PE/COFF sections?
.....

If we include the alignment in the text section, the signed binary boots
fine, and the relevant sbverify warning goes away
sbverify ./lib/efi_loader/helloworld.efi
warning: data remaining[8704 vs 12720]: gaps between PE/COFF sections?
.....

We should look into the remaining warning at some point as well
regarding the gaps between PE/COFF sections.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>