ARM: 9009/1: uncompress: Enable debug in head.S

The assembly file head.S includes some debug code that does
not get enabled when we select CONFIG_DEBUG_UNCOMPRESS.
The debug in head.S relies on the user tagging on -DDEBUG
on the compilation command line.

To simplify debugging, tag on -DDEBUG so that we also get
these debug messages when selecting CONFIG_DEBUG_UNCOMPRESS.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>