ARM: decompressor: defer loading of the contents of the LC0 structure

The remaining contents of LC0 are only used after the point in the
decompressor startup code where we enter via 'wont_overwrite'. So
move the loading of the LC0 structure after it. This will allow us
to jump to wont_overwrite directly from the EFI stub, and execute
the decompressor in place at the offset it was loaded by the UEFI
firmware.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>