rockchip: binman: Factor out arch and compression

Declare arch and compression at the top of the file to avoid needing
ifdefs in every usage.

Add a few comments to help with the remaining #ifdefs.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
1 file changed