ARM: 7672/1: uncompress debug support for multiplatform build

Instead of giving zero support of uncompress debug for multiplatform
build, the patch turns uncompress debug into one part of DEBUG_LL
support.  When DEBUG_LL is turned on for a particular platform,
uncompress debug works too for that platform.

OMAP and Tegra are exceptions here.  OMAP low-level debug code places
data in the .data section, and that is not allowed in decompressor.
And Tegra code has reference to variable that's unavailable in
decompressor but only in kernel.  That's why Kconfig symbol
DEBUG_UNCOMPRESS controlling multiplatform uncompress debug support is
defined with !DEBUG_OMAP2PLUS_UART && !DEBUG_TEGRA_UART.

It creates arch/arm/boot/compressed/debug.S with CONFIG_DEBUG_LL_INCLUDE
included there, implements a generic putc() using those macros, which
will be built when DEBUG_UNCOMPRESS is defined.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>