.gitignore: ignore more files generated for the sandbox

.gitignore: ignore more files generated for the sandbox

Change the existing regex "/capsule.*.efi-capsule" to
also ignore the following files when building the sandbox:

capsule_in.capsule1.efi-capsule
capsule_in.capsule10.efi-capsule
capsule_in.capsule11.efi-capsule
capsule_in.capsule2.efi-capsule
capsule_in.capsule3.efi-capsule
capsule_in.capsule4.efi-capsule
capsule_in.capsule5.efi-capsule
capsule_in.capsule6.efi-capsule
capsule_in.capsule7.efi-capsule
capsule_in.capsule8.efi-capsule
capsule_in.capsule9.efi-capsule

As test/overlay folder was renamed to test/fdt_overlay,
fix the related ignore entries:

test/fdt_overlay/test-fdt-overlay-stacked.dtbo.S
test/fdt_overlay/test-fdt-overlay.dtbo.S

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>